!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

disallow variable declarations from shadowing variables declared in the outer scope (no-shadow)

Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. For example:

var a = 3;
function b() {
    var a = 10;
}

In this case, the variable a inside of b() is shadowing the variable a in the global scope. This can cause confusion while reading the code and it's impossible to access the global variable.

Rule Details

This rule aims to eliminate shadowed variable declarations.

Examples of incorrect code for this rule:

/*eslint no-shadow: "error"*/
/*eslint-env es6*/

var a = 3;
function b() {
    var a = 10;
}

var b = function () {
    var a = 10;
}

function b(a) {
    a = 10;
}
b(a);

if (true) {
    let a = 5;
}

Options

This rule takes one option, an object, with properties "builtinGlobals", "hoist" and "allow".

{
    "no-shadow": ["error", { "builtinGlobals": false, "hoist": "functions", "allow": [] }]
}

builtinGlobals

The builtinGlobals option is false by default. If it is true, the rule prevents shadowing of built-in global variables: Object, Array, Number, and so on.

Examples of incorrect code for the { "builtinGlobals": true } option:

/*eslint no-shadow: ["error", { "builtinGlobals": true }]*/

function foo() {
    var Object = 0;
}

hoist

The hoist option has three settings:

• functions (by default) - reports shadowing before the outer functions are defined.
• all - reports all shadowing before the outer variables/functions are defined.
• never - never report shadowing before the outer variables/functions are defined.

hoist: functions

Examples of incorrect code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let b = 6;
}

function b() {}

Although let b in the if statement is before the function declaration in the outer scope, it is incorrect.

Examples of correct code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
}

let a = 5;

Because let a in the if statement is before the variable declaration in the outer scope, it is correct.

hoist: all

Examples of incorrect code for the { "hoist": "all" } option:

/*eslint no-shadow: ["error", { "hoist": "all" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

hoist: never

Examples of correct code for the { "hoist": "never" } option:

/*eslint no-shadow: ["error", { "hoist": "never" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

Because let a and let b in the if statement are before the declarations in the outer scope, they are correct.

allow

The allow option is an array of identifier names for which shadowing is allowed. For example, "resolve", "reject", "done", "cb".

Examples of correct code for the { "allow": ["done"] } option:

/*eslint no-shadow: ["error", { "allow": ["done"] }]*/
/*eslint-env es6*/

import async from 'async';

function foo(done) {
  async.map([1, 2], function (e, done) {
    done(null, e * 2)
  }, done);
}

foo(function (err, result) {
  console.log({ err, result });
});

Further Reading

• Variable Shadowing

Related Rules

• [no-shadow-restricted-names](no-shadow-restricted-names.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Require === and !== (eqeqeq)

It is considered good practice to use the type-safe equality operators === and !== instead of their regular counterparts == and !=.

The reason for this is that == and != do type coercion which follows the rather obscure Abstract Equality Comparison Algorithm. For instance, the following statements are all considered true:

• [] == false
• [] == ![]
• 3 == "03"

If one of those occurs in an innocent-looking statement such as a == b the actual problem is very difficult to spot.

Rule Details

This rule is aimed at eliminating the type-unsafe equality operators.

Examples of incorrect code for this rule:

/*eslint eqeqeq: "error"*/

if (x == 42) { }

if ("" == text) { }

if (obj.getStuff() != undefined) { }

The --fix option on the command line automatically fixes some problems reported by this rule. A problem is only fixed if one of the operands is a typeof expression, or if both operands are literals with the same type.

Options

always

The "always" option (default) enforces the use of === and !== in every situation (except when you opt-in to more specific handling of null [see below]).

Examples of incorrect code for the "always" option:

/*eslint eqeqeq: ["error", "always"]*/

a == b
foo == true
bananas != 1
value == undefined
typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null

Examples of correct code for the "always" option:

/*eslint eqeqeq: ["error", "always"]*/

a === b
foo === true
bananas !== 1
value === undefined
typeof foo === 'undefined'
'hello' !== 'world'
0 === 0
true === true
foo === null

This rule optionally takes a second argument, which should be an object with the following supported properties:

• "null": Customize how this rule treats null literals. Possible values:
  • always (default) - Always use === or !==.
  • never - Never use === or !== with null.
  • ignore - Do not apply this rule to null.

smart

The "smart" option enforces the use of === and !== except for these cases:

• Comparing two literal values
• Evaluating the value of typeof
• Comparing against null

Examples of incorrect code for the "smart" option:

/*eslint eqeqeq: ["error", "smart"]*/

// comparing two variables requires ===
a == b

// only one side is a literal
foo == true
bananas != 1

// comparing to undefined requires ===
value == undefined

Examples of correct code for the "smart" option:

/*eslint eqeqeq: ["error", "smart"]*/

typeof foo == 'undefined'
'hello' != 'world'
0 == 0
true == true
foo == null

allow-null

Deprecated: Instead of using this option use "always" and pass a "null" option property with value "ignore". This will tell eslint to always enforce strict equality except when comparing with the null literal.

["error", "always", {"null": "ignore"}]

When Not To Use It

If you don't want to enforce a style for using equality operators, then it's safe to disable this rule. Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

disallow variable declarations from shadowing variables declared in the outer scope (no-shadow)

Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. For example:

var a = 3;
function b() {
    var a = 10;
}

In this case, the variable a inside of b() is shadowing the variable a in the global scope. This can cause confusion while reading the code and it's impossible to access the global variable.

Rule Details

This rule aims to eliminate shadowed variable declarations.

Examples of incorrect code for this rule:

/*eslint no-shadow: "error"*/
/*eslint-env es6*/

var a = 3;
function b() {
    var a = 10;
}

var b = function () {
    var a = 10;
}

function b(a) {
    a = 10;
}
b(a);

if (true) {
    let a = 5;
}

Options

This rule takes one option, an object, with properties "builtinGlobals", "hoist" and "allow".

{
    "no-shadow": ["error", { "builtinGlobals": false, "hoist": "functions", "allow": [] }]
}

builtinGlobals

The builtinGlobals option is false by default. If it is true, the rule prevents shadowing of built-in global variables: Object, Array, Number, and so on.

Examples of incorrect code for the { "builtinGlobals": true } option:

/*eslint no-shadow: ["error", { "builtinGlobals": true }]*/

function foo() {
    var Object = 0;
}

hoist

The hoist option has three settings:

• functions (by default) - reports shadowing before the outer functions are defined.
• all - reports all shadowing before the outer variables/functions are defined.
• never - never report shadowing before the outer variables/functions are defined.

hoist: functions

Examples of incorrect code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let b = 6;
}

function b() {}

Although let b in the if statement is before the function declaration in the outer scope, it is incorrect.

Examples of correct code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
}

let a = 5;

Because let a in the if statement is before the variable declaration in the outer scope, it is correct.

hoist: all

Examples of incorrect code for the { "hoist": "all" } option:

/*eslint no-shadow: ["error", { "hoist": "all" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

hoist: never

Examples of correct code for the { "hoist": "never" } option:

/*eslint no-shadow: ["error", { "hoist": "never" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

Because let a and let b in the if statement are before the declarations in the outer scope, they are correct.

allow

The allow option is an array of identifier names for which shadowing is allowed. For example, "resolve", "reject", "done", "cb".

Examples of correct code for the { "allow": ["done"] } option:

/*eslint no-shadow: ["error", { "allow": ["done"] }]*/
/*eslint-env es6*/

import async from 'async';

function foo(done) {
  async.map([1, 2], function (e, done) {
    done(null, e * 2)
  }, done);
}

foo(function (err, result) {
  console.log({ err, result });
});

Further Reading

• Variable Shadowing

Related Rules

• [no-shadow-restricted-names](no-shadow-restricted-names.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Disallow Assignment in return Statement (no-return-assign)

One of the interesting, and sometimes confusing, aspects of JavaScript is that assignment can happen at almost any point. Because of this, an errant equals sign can end up causing assignment when the true intent was to do a comparison. This is especially true when using a return statement. For example:

function doSomething() {
    return foo = bar + 2;
}

It is difficult to tell the intent of the return statement here. It's possible that the function is meant to return the result of bar + 2, but then why is it assigning to foo? It's also possible that the intent was to use a comparison operator such as == and that this code is an error.

Because of this ambiguity, it's considered a best practice to not use assignment in return statements.

Rule Details

This rule aims to eliminate assignments from return statements. As such, it will warn whenever an assignment is found as part of return.

Options

The rule takes one option, a string, which must contain one of the following values:

• except-parens (default): Disallow assignments unless they are enclosed in parentheses.
• always: Disallow all assignments.

except-parens

This is the default option. It disallows assignments unless they are enclosed in parentheses.

Examples of incorrect code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

Examples of correct code for the default "except-parens" option:

/*eslint no-return-assign: "error"*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

function doSomething() {
    return (foo = bar + 2);
}

always

This option disallows all assignments in return statements. All assignments are treated as problems.

Examples of incorrect code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo = bar + 2;
}

function doSomething() {
    return foo += 2;
}

function doSomething() {
    return (foo = bar + 2);
}

Examples of correct code for the "always" option:

/*eslint no-return-assign: ["error", "always"]*/

function doSomething() {
    return foo == bar + 2;
}

function doSomething() {
    return foo === bar + 2;
}

When Not To Use It

If you want to allow the use of assignment operators in a return statement, then you can safely disable this rule. Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

enforce consistent spacing between keys and values in object literal properties (key-spacing)

This rule enforces spacing around the colon in object literal properties. It can verify each property individually, or it can ensure horizontal alignment of adjacent properties in an object literal.

Rule Details

This rule enforces consistent spacing between keys and values in object literal properties. In the case of long lines, it is acceptable to add a new line wherever whitespace is allowed.

Options

This rule has an object option:

• "beforeColon": false (default) disallows spaces between the key and the colon in object literals.
• "beforeColon": true requires at least one space between the key and the colon in object literals.
• "afterColon": true (default) requires at least one space between the colon and the value in object literals.
• "afterColon": false disallows spaces between the colon and the value in object literals.
• "mode": "strict" (default) enforces exactly one space before or after colons in object literals.
• "mode": "minimum" enforces one or more spaces before or after colons in object literals.
• "align": "value" enforces horizontal alignment of values in object literals.
• "align": "colon" enforces horizontal alignment of both colons and values in object literals.
• "align" with an object value allows for fine-grained spacing when values are being aligned in object literals.
• "singleLine" specifies a spacing style for single-line object literals.
• "multiLine" specifies a spacing style for multi-line object literals.

Please note that you can either use the top-level options or the grouped options (singleLine and multiLine) but not both.

beforeColon

Examples of incorrect code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo" : 42 };

Examples of correct code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo" : 42 };

afterColon

Examples of incorrect code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo":42 };

Examples of correct code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo":42 };

mode

Examples of incorrect code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat: 2 * 2
});

Examples of correct code for this rule with the { "mode": "minimum" } option:

/*eslint key-spacing: ["error", { "mode": "minimum" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

align

Examples of incorrect code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a: value,
    bcde:  42,
    fg :   foo()
};

Examples of correct code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a:    value,
    bcde: 42,

    fg: foo(),
    h:  function() {
        return this.a;
    },
    ijkl: 'Non-consecutive lines form a new group'
};

var obj = { a: "foo", longPropertyName: "bar" };

Examples of incorrect code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat   : 2 * 2
});

align

The align option can take additional configuration through the beforeColon, afterColon, mode, and on options.

If align is defined as an object, but not all of the parameters are provided, undefined parameters will default to the following:

// Defaults
align: {
    "beforeColon": false,
    "afterColon": true,
    "on": "colon",
    "mode": "strict"
}

Examples of correct code for this rule with sample { "align": { } } options:

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "one"   : 1,
    "seven" : 7
}

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": false,
        "afterColon": false,
        "on": "value"
    }
}]*/

var obj = {
    "one":  1,
    "seven":7
}

align and multiLine

The multiLine and align options can differ, which allows for fine-tuned control over the key-spacing of your files. align will not inherit from multiLine if align is configured as an object.

multiLine is used any time an object literal spans multiple lines. The align configuration is used when there is a group of properties in the same object. For example:

var myObj = {
  key1: 1, // uses multiLine

  key2: 2, // uses align (when defined)
  key3: 3, // uses align (when defined)

  key4: 4 // uses multiLine
}

Examples of incorrect code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon":true
    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
    },
    "one"             : 1,
    "seven"           : 7
}

Examples of correct code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon": true

    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
        //
    }, // These are two separate groups, so no alignment between `myObjectFuction` and `one`
    "one"   : 1,
    "seven" : 7 // `one` and `seven` are in their own group, and therefore aligned
}

singleLine and multiLine

Examples of correct code for this rule with sample { "singleLine": { }, "multiLine": { } } options:

/*eslint "key-spacing": [2, {
    "singleLine": {
        "beforeColon": false,
        "afterColon": true
    },
    "multiLine": {
        "beforeColon": true,
        "afterColon": true,
        "align": "colon"
    }
}]*/
var obj = { one: 1, "two": 2, three: 3 };
var obj2 = {
    "two" : 2,
    three : 3
};

When Not To Use It

If you have another convention for property spacing that might not be consistent with the available options, or if you want to permit multiple styles concurrently you can safely disable this rule. Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Disallow use of the void operator. (no-void)

The void operator takes an operand and returns undefined: void expression will evaluate expression and return undefined. It can be used to ignore any side effects expression may produce:

The common case of using void operator is to get a "pure" undefined value as prior to ES5 the undefined variable was mutable:

// will always return undefined
(function(){
    return void 0;
})();

// will return 1 in ES3 and undefined in ES5+
(function(){
    undefined = 1;
    return undefined;
})();

// will throw TypeError in ES5+
(function(){
    'use strict';
    undefined = 1;
})();

Another common case is to minify code as void 0 is shorter than undefined:

foo = void 0;
foo = undefined;

When used with IIFE (immediately-invoked function expression), void can be used to force the function keyword to be treated as an expression instead of a declaration:

var foo = 1;
void function(){ foo = 1; }() // will assign foo a value of 1
+function(){ foo = 1; }() // same as above

function(){ foo = 1; }() // will throw SyntaxError

Some code styles prohibit void operator, marking it as non-obvious and hard to read.

Rule Details

This rule aims to eliminate use of void operator.

Examples of incorrect code for this rule:

/*eslint no-void: "error"*/

void foo

var foo = void bar();

When Not To Use It

If you intentionally use the void operator then you can disable this rule.

Further Reading

• Mozilla Developer Network
• Bad Parts: Appendix B - JavaScript: The Good Parts by Douglas Crockford

Related Rules

• [no-undef-init](no-undef-init.md)
• [no-undefined](no-undefined.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Require Or Disallow Space Before Blocks (space-before-blocks)

Consistency is an important part of any style guide. While it is a personal preference where to put the opening brace of blocks, it should be consistent across a whole project. Having an inconsistent style distracts the reader from seeing the important parts of the code.

Rule Details

This rule will enforce consistency of spacing before blocks. It is only applied on blocks that don’t begin on a new line.

• This rule ignores spacing which is between => and a block. The spacing is handled by the arrow-spacing rule.
• This rule ignores spacing which is between a keyword and a block. The spacing is handled by the keyword-spacing rule.

Options

This rule takes one argument. If it is "always" then blocks must always have at least one preceding space. If "never" then all blocks should never have any preceding space. If different spacing is desired for function blocks, keyword blocks and classes, an optional configuration object can be passed as the rule argument to configure the cases separately.

( e.g. { "functions": "never", "keywords": "always", "classes": "always" } )

The default is "always".

"always"

Examples of incorrect code for this rule with the "always" option:

/*eslint space-before-blocks: "error"*/

if (a){
    b();
}

function a(){}

for (;;){
    b();
}

try {} catch(a){}

class Foo{
  constructor(){}
}

Examples of correct code for this rule with the "always" option:

/*eslint space-before-blocks: "error"*/

if (a) {
    b();
}

if (a) {
    b();
} else{ /*no error. this is checked by `keyword-spacing` rule.*/
    c();
}


function a() {}

for (;;) {
    b();
}

try {} catch(a) {}

"never"

Examples of incorrect code for this rule with the "never" option:

/*eslint space-before-blocks: ["error", "never"]*/

if (a) {
    b();
}

function a() {}

for (;;) {
    b();
}

try {} catch(a) {}

Examples of correct code for this rule with the "never" option:

/*eslint space-before-blocks: ["error", "never"]*/

if (a){
    b();
}

function a(){}

for (;;){
    b();
}

try{} catch(a){}

class Foo{
  constructor(){}
}

Examples of incorrect code for this rule when configured { "functions": "never", "keywords": "always", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "always", "classes": "never" }]*/
/*eslint-env es6*/

function a() {}

try {} catch(a){}

class Foo{
  constructor() {}
}

Examples of correct code for this rule when configured { "functions": "never", "keywords": "always", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "always", "classes": "never" }]*/
/*eslint-env es6*/

for (;;) {
  // ...
}

describe(function(){
  // ...
});

class Foo {
  constructor(){}
}

Examples of incorrect code for this rule when configured { "functions": "always", "keywords": "never", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "always", "keywords": "never", "classes": "never" }]*/
/*eslint-env es6*/

function a(){}

try {} catch(a) {}

class Foo {
  constructor(){}
}

Examples of correct code for this rule when configured { "functions": "always", "keywords": "never", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "always", "keywords": "never", "classes": "never" }]*/
/*eslint-env es6*/

if (a){
  b();
}

var a = function() {}

class Foo{
  constructor() {}
}

Examples of incorrect code for this rule when configured { "functions": "never", "keywords": "never", "classes": "always" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "never", "classes": "always" }]*/
/*eslint-env es6*/

class Foo{
  constructor(){}
}

Examples of correct code for this rule when configured { "functions": "never", "keywords": "never", "classes": "always" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "never", "classes": "always" }]*/
/*eslint-env es6*/

class Foo {
  constructor(){}
}

When Not To Use It

You can turn this rule off if you are not concerned with the consistency of spacing before blocks.

Related Rules

• [keyword-spacing](keyword-spacing.md)
• [arrow-spacing](arrow-spacing.md)
• [brace-style](brace-style.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

disallow variable declarations from shadowing variables declared in the outer scope (no-shadow)

Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. For example:

var a = 3;
function b() {
    var a = 10;
}

In this case, the variable a inside of b() is shadowing the variable a in the global scope. This can cause confusion while reading the code and it's impossible to access the global variable.

Rule Details

This rule aims to eliminate shadowed variable declarations.

Examples of incorrect code for this rule:

/*eslint no-shadow: "error"*/
/*eslint-env es6*/

var a = 3;
function b() {
    var a = 10;
}

var b = function () {
    var a = 10;
}

function b(a) {
    a = 10;
}
b(a);

if (true) {
    let a = 5;
}

Options

This rule takes one option, an object, with properties "builtinGlobals", "hoist" and "allow".

{
    "no-shadow": ["error", { "builtinGlobals": false, "hoist": "functions", "allow": [] }]
}

builtinGlobals

The builtinGlobals option is false by default. If it is true, the rule prevents shadowing of built-in global variables: Object, Array, Number, and so on.

Examples of incorrect code for the { "builtinGlobals": true } option:

/*eslint no-shadow: ["error", { "builtinGlobals": true }]*/

function foo() {
    var Object = 0;
}

hoist

The hoist option has three settings:

• functions (by default) - reports shadowing before the outer functions are defined.
• all - reports all shadowing before the outer variables/functions are defined.
• never - never report shadowing before the outer variables/functions are defined.

hoist: functions

Examples of incorrect code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let b = 6;
}

function b() {}

Although let b in the if statement is before the function declaration in the outer scope, it is incorrect.

Examples of correct code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
}

let a = 5;

Because let a in the if statement is before the variable declaration in the outer scope, it is correct.

hoist: all

Examples of incorrect code for the { "hoist": "all" } option:

/*eslint no-shadow: ["error", { "hoist": "all" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

hoist: never

Examples of correct code for the { "hoist": "never" } option:

/*eslint no-shadow: ["error", { "hoist": "never" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

Because let a and let b in the if statement are before the declarations in the outer scope, they are correct.

allow

The allow option is an array of identifier names for which shadowing is allowed. For example, "resolve", "reject", "done", "cb".

Examples of correct code for the { "allow": ["done"] } option:

/*eslint no-shadow: ["error", { "allow": ["done"] }]*/
/*eslint-env es6*/

import async from 'async';

function foo(done) {
  async.map([1, 2], function (e, done) {
    done(null, e * 2)
  }, done);
}

foo(function (err, result) {
  console.log({ err, result });
});

Further Reading

• Variable Shadowing

Related Rules

• [no-shadow-restricted-names](no-shadow-restricted-names.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

disallow variable declarations from shadowing variables declared in the outer scope (no-shadow)

Shadowing is the process by which a local variable shares the same name as a variable in its containing scope. For example:

var a = 3;
function b() {
    var a = 10;
}

In this case, the variable a inside of b() is shadowing the variable a in the global scope. This can cause confusion while reading the code and it's impossible to access the global variable.

Rule Details

This rule aims to eliminate shadowed variable declarations.

Examples of incorrect code for this rule:

/*eslint no-shadow: "error"*/
/*eslint-env es6*/

var a = 3;
function b() {
    var a = 10;
}

var b = function () {
    var a = 10;
}

function b(a) {
    a = 10;
}
b(a);

if (true) {
    let a = 5;
}

Options

This rule takes one option, an object, with properties "builtinGlobals", "hoist" and "allow".

{
    "no-shadow": ["error", { "builtinGlobals": false, "hoist": "functions", "allow": [] }]
}

builtinGlobals

The builtinGlobals option is false by default. If it is true, the rule prevents shadowing of built-in global variables: Object, Array, Number, and so on.

Examples of incorrect code for the { "builtinGlobals": true } option:

/*eslint no-shadow: ["error", { "builtinGlobals": true }]*/

function foo() {
    var Object = 0;
}

hoist

The hoist option has three settings:

• functions (by default) - reports shadowing before the outer functions are defined.
• all - reports all shadowing before the outer variables/functions are defined.
• never - never report shadowing before the outer variables/functions are defined.

hoist: functions

Examples of incorrect code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let b = 6;
}

function b() {}

Although let b in the if statement is before the function declaration in the outer scope, it is incorrect.

Examples of correct code for the default { "hoist": "functions" } option:

/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
}

let a = 5;

Because let a in the if statement is before the variable declaration in the outer scope, it is correct.

hoist: all

Examples of incorrect code for the { "hoist": "all" } option:

/*eslint no-shadow: ["error", { "hoist": "all" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

hoist: never

Examples of correct code for the { "hoist": "never" } option:

/*eslint no-shadow: ["error", { "hoist": "never" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

Because let a and let b in the if statement are before the declarations in the outer scope, they are correct.

allow

The allow option is an array of identifier names for which shadowing is allowed. For example, "resolve", "reject", "done", "cb".

Examples of correct code for the { "allow": ["done"] } option:

/*eslint no-shadow: ["error", { "allow": ["done"] }]*/
/*eslint-env es6*/

import async from 'async';

function foo(done) {
  async.map([1, 2], function (e, done) {
    done(null, e * 2)
  }, done);
}

foo(function (err, result) {
  console.log({ err, result });
});

Further Reading

• Variable Shadowing

Related Rules

• [no-shadow-restricted-names](no-shadow-restricted-names.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Require Or Disallow Space Before Blocks (space-before-blocks)

Consistency is an important part of any style guide. While it is a personal preference where to put the opening brace of blocks, it should be consistent across a whole project. Having an inconsistent style distracts the reader from seeing the important parts of the code.

Rule Details

This rule will enforce consistency of spacing before blocks. It is only applied on blocks that don’t begin on a new line.

• This rule ignores spacing which is between => and a block. The spacing is handled by the arrow-spacing rule.
• This rule ignores spacing which is between a keyword and a block. The spacing is handled by the keyword-spacing rule.

Options

This rule takes one argument. If it is "always" then blocks must always have at least one preceding space. If "never" then all blocks should never have any preceding space. If different spacing is desired for function blocks, keyword blocks and classes, an optional configuration object can be passed as the rule argument to configure the cases separately.

( e.g. { "functions": "never", "keywords": "always", "classes": "always" } )

The default is "always".

"always"

Examples of incorrect code for this rule with the "always" option:

/*eslint space-before-blocks: "error"*/

if (a){
    b();
}

function a(){}

for (;;){
    b();
}

try {} catch(a){}

class Foo{
  constructor(){}
}

Examples of correct code for this rule with the "always" option:

/*eslint space-before-blocks: "error"*/

if (a) {
    b();
}

if (a) {
    b();
} else{ /*no error. this is checked by `keyword-spacing` rule.*/
    c();
}


function a() {}

for (;;) {
    b();
}

try {} catch(a) {}

"never"

Examples of incorrect code for this rule with the "never" option:

/*eslint space-before-blocks: ["error", "never"]*/

if (a) {
    b();
}

function a() {}

for (;;) {
    b();
}

try {} catch(a) {}

Examples of correct code for this rule with the "never" option:

/*eslint space-before-blocks: ["error", "never"]*/

if (a){
    b();
}

function a(){}

for (;;){
    b();
}

try{} catch(a){}

class Foo{
  constructor(){}
}

Examples of incorrect code for this rule when configured { "functions": "never", "keywords": "always", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "always", "classes": "never" }]*/
/*eslint-env es6*/

function a() {}

try {} catch(a){}

class Foo{
  constructor() {}
}

Examples of correct code for this rule when configured { "functions": "never", "keywords": "always", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "always", "classes": "never" }]*/
/*eslint-env es6*/

for (;;) {
  // ...
}

describe(function(){
  // ...
});

class Foo {
  constructor(){}
}

Examples of incorrect code for this rule when configured { "functions": "always", "keywords": "never", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "always", "keywords": "never", "classes": "never" }]*/
/*eslint-env es6*/

function a(){}

try {} catch(a) {}

class Foo {
  constructor(){}
}

Examples of correct code for this rule when configured { "functions": "always", "keywords": "never", "classes": "never" }:

/*eslint space-before-blocks: ["error", { "functions": "always", "keywords": "never", "classes": "never" }]*/
/*eslint-env es6*/

if (a){
  b();
}

var a = function() {}

class Foo{
  constructor() {}
}

Examples of incorrect code for this rule when configured { "functions": "never", "keywords": "never", "classes": "always" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "never", "classes": "always" }]*/
/*eslint-env es6*/

class Foo{
  constructor(){}
}

Examples of correct code for this rule when configured { "functions": "never", "keywords": "never", "classes": "always" }:

/*eslint space-before-blocks: ["error", { "functions": "never", "keywords": "never", "classes": "always" }]*/
/*eslint-env es6*/

class Foo {
  constructor(){}
}

When Not To Use It

You can turn this rule off if you are not concerned with the consistency of spacing before blocks.

Related Rules

• [keyword-spacing](keyword-spacing.md)
• [arrow-spacing](arrow-spacing.md)
• [brace-style](brace-style.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforce spacing before and after semicolons (semi-spacing)

JavaScript allows you to place unnecessary spaces before or after a semicolon.

Disallowing or enforcing space around a semicolon can improve the readability of your program.

var a = "b" ;

var c = "d";var e = "f";

Rule Details

This rule aims to enforce spacing around a semicolon. This rule prevents the use of spaces before a semicolon in expressions.

This rule doesn't check spacing in the following cases:

• The spacing after the semicolon if it is the first token in the line.

• The spacing before the semicolon if it is after an opening parenthesis (( or {), or the spacing after the semicolon if it is before a closing parenthesis () or }). That spacing is checked by space-in-parens or block-spacing.

• The spacing around the semicolon in a for loop with an empty condition (for(;;)).

Options

The rule takes one option, an object, which has two keys before and after having boolean values true or false. If before is true, space is enforced before semicolons and if it's false, space is disallowed before semicolons. If after is true, space is enforced after semicolons and if it's false, space is disallowed after semicolons. The after option will be only applied if a semicolon is not at the end of line.

The default is {"before": false, "after": true}.

"semi-spacing": ["error", {"before": false, "after": true}]

{"before": false, "after": true}

This is the default option. It enforces spacing after semicolons and disallows spacing before semicolons.

Examples of incorrect code for this rule:

/*eslint semi-spacing: "error"*/

var foo ;
var foo;var bar;
throw new Error("error") ;
while (a) { break ; }
for (i = 0 ; i < 10 ; i++) {}
for (i = 0;i < 10;i++) {}

Examples of correct code for this rule:

/*eslint semi-spacing: "error"*/

var foo;
var foo; var bar;
throw new Error("error");
while (a) { break; }
for (i = 0; i < 10; i++) {}
for (;;) {}
if (true) {;}
;foo();

{"before": true, "after": false}

This option enforces spacing before semicolons and disallows spacing after semicolons.

Examples of incorrect code for this rule with the {"before": true, "after": false} option:

/*eslint semi-spacing: ["error", { "before": true, "after": false }]*/

var foo;
var foo ; var bar;
throw new Error("error");
while (a) { break; }
for (i = 0;i < 10;i++) {}
for (i = 0; i < 10; i++) {}

Examples of correct code for this rule with the {"before": true, "after": false} option:

/*eslint semi-spacing: ["error", { "before": true, "after": false }]*/

var foo ;
var foo ;var bar ;
throw new Error("error") ;
while (a) {break ;}
for (i = 0 ;i < 10 ;i++) {}

When Not To Use It

You can turn this rule off if you are not concerned with the consistency of spacing before or after semicolons.

Related Rules

• [semi](semi.md)
• [no-extra-semi](no-extra-semi.md)
• [comma-spacing](comma-spacing.md)
• [block-spacing](block-spacing.md)
• [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

Enforces spacing around commas (comma-spacing)

Spacing around commas improve readability of a list of items. Although most of the style guidelines for languages prescribe adding a space after a comma and not before it, it is subjective to the preferences of a project.

var foo = 1, bar = 2;
var foo = 1 ,bar = 2;

Rule Details

This rule enforces consistent spacing before and after commas in variable declarations, array literals, object literals, function parameters, and sequences.

This rule does not apply in an ArrayExpression or ArrayPattern in either of the following cases:

• adjacent null elements
• an initial null element, to avoid conflicts with the [array-bracket-spacing](array-bracket-spacing.md) rule

Options

This rule has an object option:

• "before": false (default) disallows spaces before commas
• "before": true requires one or more spaces before commas
• "after": true (default) requires one or more spaces after commas
• "after": false disallows spaces after commas

after

Examples of incorrect code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1 ,bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/

var foo = 1, bar = 2
    , baz = 3;
var arr = [1, 2];
var arr = [1,, 3]
var obj = {"foo": "bar", "baz": "qur"};
foo(a, b);
new Foo(a, b);
function foo(a, b){}
a, b

Example of correct code for this rule with initial null element for the default { "before": false, "after": true } options:

/*eslint comma-spacing: ["error", { "before": false, "after": true }]*/
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [ , 2, 3 ]

before

Examples of incorrect code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1, bar = 2;
var arr = [1 , 2];
var obj = {"foo": "bar", "baz": "qur"};
new Foo(a,b);
function foo(a,b){}
a, b

Examples of correct code for this rule with the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/

var foo = 1 ,bar = 2 ,
    baz = true;
var arr = [1 ,2];
var arr = [1 ,,3]
var obj = {"foo": "bar" ,"baz": "qur"};
foo(a ,b);
new Foo(a ,b);
function foo(a ,b){}
a ,b

Examples of correct code for this rule with initial null element for the { "before": true, "after": false } options:

/*eslint comma-spacing: ["error", { "before": true, "after": false }]*/
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [,2 ,3]

When Not To Use It

If your project will not be following a consistent comma-spacing pattern, turn this rule off.

Further Reading

• Javascript
• Dojo Style Guide

Related Rules

• [array-bracket-spacing](array-bracket-spacing.md)
• [comma-style](comma-style.md)
• [space-in-brackets](space-in-brackets.md) (deprecated)
• [space-in-parens](space-in-parens.md)
• [space-infix-ops](space-infix-ops.md)
• [space-after-keywords](space-after-keywords)
• [space-unary-ops](space-unary-ops)
• [space-return-throw-case](space-return-throw-case) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

require or disallow semicolons instead of ASI (semi)

JavaScript is unique amongst the C-like languages in that it doesn't require semicolons at the end of each statement. In many cases, the JavaScript engine can determine that a semicolon should be in a certain spot and will automatically add it. This feature is known as automatic semicolon insertion (ASI) and is considered one of the more controversial features of JavaScript. For example, the following lines are both valid:

var name = "ESLint"
var website = "eslint.org";

On the first line, the JavaScript engine will automatically insert a semicolon, so this is not considered a syntax error. The JavaScript engine still knows how to interpret the line and knows that the line end indicates the end of the statement.

In the debate over ASI, there are generally two schools of thought. The first is that we should treat ASI as if it didn't exist and always include semicolons manually. The rationale is that it's easier to always include semicolons than to try to remember when they are or are not required, and thus decreases the possibility of introducing an error.

However, the ASI mechanism can sometimes be tricky to people who are using semicolons. For example, consider this code:

return
{
    name: "ESLint"
};

This may look like a return statement that returns an object literal, however, the JavaScript engine will interpret this code as:

return;
{
    name: "ESLint";
}

Effectively, a semicolon is inserted after the return statement, causing the code below it (a labeled literal inside a block) to be unreachable. This rule and the [no-unreachable](no-unreachable.md) rule will protect your code from such cases.

On the other side of the argument are those who says that since semicolons are inserted automatically, they are optional and do not need to be inserted manually. However, the ASI mechanism can also be tricky to people who don't use semicolons. For example, consider this code:

var globalCounter = { }

(function () {
    var n = 0
    globalCounter.increment = function () {
        return ++n
    }
})()

In this example, a semicolon will not be inserted after the first line, causing a run-time error (because an empty object is called as if it's a function). The [no-unexpected-multiline](no-unexpected-multiline.md) rule can protect your code from such cases.

Although ASI allows for more freedom over your coding style, it can also make your code behave in an unexpected way, whether you use semicolons or not. Therefore, it is best to know when ASI takes place and when it does not, and have ESLint protect your code from these potentially unexpected cases. In short, as once described by Isaac Schlueter, a \n character always ends a statement (just like a semicolon) unless one of the following is true:

1. The statement has an unclosed paren, array literal, or object literal or ends in some other way that is not a valid way to end a statement. (For instance, ending with . or ,.)
2. The line is -- or ++ (in which case it will decrement/increment the next token.)
3. It is a for(), while(), do, if(), or else, and there is no {
4. The next line starts with [, (, +, *, /, -, ,, ., or some other binary operator that can only be found between two tokens in a single expression.

Rule Details

This rule enforces consistent use of semicolons.

Options

This rule has two options, a string option and an object option.

String option:

• "always" (default) requires semicolons at the end of statements
• "never" disallows semicolons as the end of statements (except to disambiguate statements beginning with [, (, /, +, or -)

Object option:

• "omitLastInOneLineBlock": true ignores the last semicolon in a block in which its braces (and therefore the content of the block) are in the same line

always

Examples of incorrect code for this rule with the default "always" option:

/*eslint semi: ["error", "always"]*/

var name = "ESLint"

object.method = function() {
    // ...
}

Examples of correct code for this rule with the default "always" option:

/*eslint semi: "error"*/

var name = "ESLint";

object.method = function() {
    // ...
};

never

Examples of incorrect code for this rule with the "never" option:

/*eslint semi: ["error", "never"]*/

var name = "ESLint";

object.method = function() {
    // ...
};

Examples of correct code for this rule with the "never" option:

/*eslint semi: ["error", "never"]*/

var name = "ESLint"

object.method = function() {
    // ...
}

var name = "ESLint"

;(function() {
    // ...
})()

omitLastInOneLineBlock

Examples of additional correct code for this rule with the "always", { "omitLastInOneLineBlock": true } options:

/*eslint semi: ["error", "always", { "omitLastInOneLineBlock": true}] */

if (foo) { bar() }

if (foo) { bar(); baz() }

When Not To Use It

If you do not want to enforce semicolon usage (or omission) in any particular way, then you can turn this rule off.

Further Reading

• An Open Letter to JavaScript Leaders Regarding Semicolons
• JavaScript Semicolon Insertion

Related Rules

• [no-extra-semi](no-extra-semi.md)
• [no-unexpected-multiline](no-unexpected-multiline.md)
• [semi-spacing](semi-spacing.md) Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

enforce consistent spacing between keys and values in object literal properties (key-spacing)

This rule enforces spacing around the colon in object literal properties. It can verify each property individually, or it can ensure horizontal alignment of adjacent properties in an object literal.

Rule Details

This rule enforces consistent spacing between keys and values in object literal properties. In the case of long lines, it is acceptable to add a new line wherever whitespace is allowed.

Options

This rule has an object option:

• "beforeColon": false (default) disallows spaces between the key and the colon in object literals.
• "beforeColon": true requires at least one space between the key and the colon in object literals.
• "afterColon": true (default) requires at least one space between the colon and the value in object literals.
• "afterColon": false disallows spaces between the colon and the value in object literals.
• "mode": "strict" (default) enforces exactly one space before or after colons in object literals.
• "mode": "minimum" enforces one or more spaces before or after colons in object literals.
• "align": "value" enforces horizontal alignment of values in object literals.
• "align": "colon" enforces horizontal alignment of both colons and values in object literals.
• "align" with an object value allows for fine-grained spacing when values are being aligned in object literals.
• "singleLine" specifies a spacing style for single-line object literals.
• "multiLine" specifies a spacing style for multi-line object literals.

Please note that you can either use the top-level options or the grouped options (singleLine and multiLine) but not both.

beforeColon

Examples of incorrect code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo" : 42 };

Examples of correct code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo" : 42 };

afterColon

Examples of incorrect code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo":42 };

Examples of correct code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo":42 };

mode

Examples of incorrect code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat: 2 * 2
});

Examples of correct code for this rule with the { "mode": "minimum" } option:

/*eslint key-spacing: ["error", { "mode": "minimum" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

align

Examples of incorrect code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a: value,
    bcde:  42,
    fg :   foo()
};

Examples of correct code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a:    value,
    bcde: 42,

    fg: foo(),
    h:  function() {
        return this.a;
    },
    ijkl: 'Non-consecutive lines form a new group'
};

var obj = { a: "foo", longPropertyName: "bar" };

Examples of incorrect code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat   : 2 * 2
});

align

The align option can take additional configuration through the beforeColon, afterColon, mode, and on options.

If align is defined as an object, but not all of the parameters are provided, undefined parameters will default to the following:

// Defaults
align: {
    "beforeColon": false,
    "afterColon": true,
    "on": "colon",
    "mode": "strict"
}

Examples of correct code for this rule with sample { "align": { } } options:

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "one"   : 1,
    "seven" : 7
}

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": false,
        "afterColon": false,
        "on": "value"
    }
}]*/

var obj = {
    "one":  1,
    "seven":7
}

align and multiLine

The multiLine and align options can differ, which allows for fine-tuned control over the key-spacing of your files. align will not inherit from multiLine if align is configured as an object.

multiLine is used any time an object literal spans multiple lines. The align configuration is used when there is a group of properties in the same object. For example:

var myObj = {
  key1: 1, // uses multiLine

  key2: 2, // uses align (when defined)
  key3: 3, // uses align (when defined)

  key4: 4 // uses multiLine
}

Examples of incorrect code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon":true
    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
    },
    "one"             : 1,
    "seven"           : 7
}

Examples of correct code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon": true

    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
        //
    }, // These are two separate groups, so no alignment between `myObjectFuction` and `one`
    "one"   : 1,
    "seven" : 7 // `one` and `seven` are in their own group, and therefore aligned
}

singleLine and multiLine

Examples of correct code for this rule with sample { "singleLine": { }, "multiLine": { } } options:

/*eslint "key-spacing": [2, {
    "singleLine": {
        "beforeColon": false,
        "afterColon": true
    },
    "multiLine": {
        "beforeColon": true,
        "afterColon": true,
        "align": "colon"
    }
}]*/
var obj = { one: 1, "two": 2, three: 3 };
var obj2 = {
    "two" : 2,
    three : 3
};

When Not To Use It

If you have another convention for property spacing that might not be consistent with the available options, or if you want to permit multiple styles concurrently you can safely disable this rule. Source: http://eslint.org/docs/rules/

!function(e){function t(e){Object.defineProperty(this,e,{enumerable:!0,get:function(){return this[v][e]}})}function r(e){if("undefined"!=typeof System&&System.isModule?System.isModule(e):"[object Module]"===Object.prototype.toString.call(e))return e;var t={default:e,__useDefault:e};if(e&&e.__esModule)for(var r in e)Object.hasOwnProperty.call(e,r)&&(t[r]=e[r]);return new o(t)}function o(e){Object.defineProperty(this,v,{value:e}),Object.keys(e).forEach(t,this)}function n(e){return"@node/"===e.substr(0,6)?c(e,r(m(e.substr(6))),{}):p[e]}function u(e){var t=n(e);if(!t)throw new Error('Module "'+e+'" expected, but not contained in build.');if(t.module)return t.module;var r=t.linkRecord;return i(t,r),a(t,r,[]),t.module}function i(e,t){if(!t.depLoads){t.declare&&d(e,t),t.depLoads=[];for(var r=0;r<t.deps.length;r++){var o=n(t.deps[r]);t.depLoads.push(o),o.linkRecord&&i(o,o.linkRecord);var u=t.setters&&t.setters[r];u&&(u(o.module||o.linkRecord.moduleObj),o.importerSetters.push(u))}return e}}function d(t,r){var o=r.moduleObj,n=t.importerSetters,u=!1,i=r.declare.call(e,function(e,t){if(!u){if("object"==typeof e)for(var r in e)"__useDefault"!==r&&(o[r]=e[r]);else o[e]=t;u=!0;for(var i=0;i<n.length;i++)n[i](o);return u=!1,t}},{id:t.key});"function"!=typeof i?(r.setters=i.setters,r.execute=i.execute):(r.setters=[],r.execute=i)}function l(e,t,r){return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:r,setters:void 0,execute:void 0,moduleObj:{}}}}function f(e,t,r,o){var n={};return p[e]={key:e,module:void 0,importerSetters:[],linkRecord:{deps:t,depLoads:void 0,declare:void 0,execute:o,executingRequire:r,moduleObj:{default:n,__useDefault:n},setters:void 0}}}function s(e,t,r){return function(o){for(var n=0;n<e.length;n++)if(e[n]===o){var u,i=t[n],d=i.linkRecord;return u=d?-1===r.indexOf(i)?a(i,d,r):d.moduleObj:i.module,"__useDefault"in u?u.__useDefault:u}}}function a(t,r,n){if(n.push(t),t.module)return t.module;var u;if(r.setters){for(var i=0;i<r.deps.length;i++){var d=r.depLoads[i],l=d.linkRecord;l&&-1===n.indexOf(d)&&(u=a(d,l,l.setters?n:[]))}r.execute.call(y)}else{var f={id:t.key},c=r.moduleObj;Object.defineProperty(f,"exports",{configurable:!0,set:function(e){c.default=c.__useDefault=e},get:function(){return c.__useDefault}});var p=s(r.deps,r.depLoads,n);if(!r.executingRequire)for(var i=0;i<r.deps.length;i++)p(r.deps[i]);var v=r.execute.call(e,p,c.__useDefault,f);void 0!==v?c.default=c.__useDefault=v:f.exports!==c.__useDefault&&(c.default=c.__useDefault=f.exports);var m=c.__useDefault;if(m&&m.__esModule)for(var b in m)Object.hasOwnProperty.call(m,b)&&(c[b]=m[b])}var f=t.module=new o(r.moduleObj);if(!r.setters)for(var i=0;i<t.importerSetters.length;i++)t.importerSetters[i](f);return f}function c(e,t){return p[e]={key:e,module:t,importerSetters:[],linkRecord:void 0}}var p={},v="undefined"!=typeof Symbol?Symbol():"@@baseObject";o.prototype=Object.create(null),"undefined"!=typeof Symbol&&Symbol.toStringTag&&(o.prototype[Symbol.toStringTag]="Module");var m="undefined"!=typeof System&&System._nodeRequire||"undefined"!=typeof require&&"undefined"!=typeof require.resolve&&"undefined"!=typeof process&&process.platform&&require,y={};return Object.freeze&&Object.freeze(y),function(e,t,n,i){return function(d){d(function(d){var s={_nodeRequire:m,register:l,registerDynamic:f,registry:{get:function(e){return p[e].module},set:c},newModule:function(e){return new o(e)}};c("@empty",new o({}));for(var a=0;a<t.length;a++)c(t[a],r(arguments[a],{}));i(s);var v=u(e[0]);if(e.length>1)for(var a=1;a<e.length;a++)u(e[a]);return n?v.__useDefault:(v instanceof o&&Object.defineProperty(v,"__esModule",{value:!0}),v)})}}}("undefined"!=typeof self?self:"undefined"!=typeof global?global:this)

Close

enforce consistent spacing between keys and values in object literal properties (key-spacing)

This rule enforces spacing around the colon in object literal properties. It can verify each property individually, or it can ensure horizontal alignment of adjacent properties in an object literal.

Rule Details

This rule enforces consistent spacing between keys and values in object literal properties. In the case of long lines, it is acceptable to add a new line wherever whitespace is allowed.

Options

This rule has an object option:

• "beforeColon": false (default) disallows spaces between the key and the colon in object literals.
• "beforeColon": true requires at least one space between the key and the colon in object literals.
• "afterColon": true (default) requires at least one space between the colon and the value in object literals.
• "afterColon": false disallows spaces between the colon and the value in object literals.
• "mode": "strict" (default) enforces exactly one space before or after colons in object literals.
• "mode": "minimum" enforces one or more spaces before or after colons in object literals.
• "align": "value" enforces horizontal alignment of values in object literals.
• "align": "colon" enforces horizontal alignment of both colons and values in object literals.
• "align" with an object value allows for fine-grained spacing when values are being aligned in object literals.
• "singleLine" specifies a spacing style for single-line object literals.
• "multiLine" specifies a spacing style for multi-line object literals.

Please note that you can either use the top-level options or the grouped options (singleLine and multiLine) but not both.

beforeColon

Examples of incorrect code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo" : 42 };

Examples of correct code for this rule with the default { "beforeColon": false } option:

/*eslint key-spacing: ["error", { "beforeColon": false }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "beforeColon": true } option:

/*eslint key-spacing: ["error", { "beforeColon": true }]*/

var obj = { "foo" : 42 };

afterColon

Examples of incorrect code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo":42 };

Examples of correct code for this rule with the default { "afterColon": true } option:

/*eslint key-spacing: ["error", { "afterColon": true }]*/

var obj = { "foo": 42 };

Examples of incorrect code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo": 42 };

Examples of correct code for this rule with the { "afterColon": false } option:

/*eslint key-spacing: ["error", { "afterColon": false }]*/

var obj = { "foo":42 };

mode

Examples of incorrect code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the default { "mode": "strict" } option:

/*eslint key-spacing: ["error", { "mode": "strict" }]*/

call({
    foobar: 42,
    bat: 2 * 2
});

Examples of correct code for this rule with the { "mode": "minimum" } option:

/*eslint key-spacing: ["error", { "mode": "minimum" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

align

Examples of incorrect code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a: value,
    bcde:  42,
    fg :   foo()
};

Examples of correct code for this rule with the { "align": "value" } option:

/*eslint key-spacing: ["error", { "align": "value" }]*/

var obj = {
    a:    value,
    bcde: 42,

    fg: foo(),
    h:  function() {
        return this.a;
    },
    ijkl: 'Non-consecutive lines form a new group'
};

var obj = { a: "foo", longPropertyName: "bar" };

Examples of incorrect code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat:    2 * 2
});

Examples of correct code for this rule with the { "align": "colon" } option:

/*eslint key-spacing: ["error", { "align": "colon" }]*/

call({
    foobar: 42,
    bat   : 2 * 2
});

align

The align option can take additional configuration through the beforeColon, afterColon, mode, and on options.

If align is defined as an object, but not all of the parameters are provided, undefined parameters will default to the following:

// Defaults
align: {
    "beforeColon": false,
    "afterColon": true,
    "on": "colon",
    "mode": "strict"
}

Examples of correct code for this rule with sample { "align": { } } options:

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "one"   : 1,
    "seven" : 7
}

/*eslint key-spacing: ["error", {
    "align": {
        "beforeColon": false,
        "afterColon": false,
        "on": "value"
    }
}]*/

var obj = {
    "one":  1,
    "seven":7
}

align and multiLine

The multiLine and align options can differ, which allows for fine-tuned control over the key-spacing of your files. align will not inherit from multiLine if align is configured as an object.

multiLine is used any time an object literal spans multiple lines. The align configuration is used when there is a group of properties in the same object. For example:

var myObj = {
  key1: 1, // uses multiLine

  key2: 2, // uses align (when defined)
  key3: 3, // uses align (when defined)

  key4: 4 // uses multiLine
}

Examples of incorrect code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon":true
    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
    },
    "one"             : 1,
    "seven"           : 7
}

Examples of correct code for this rule with sample { "align": { }, "multiLine": { } } options:

/*eslint key-spacing: ["error", {
    "multiLine": {
        "beforeColon": false,
        "afterColon": true

    },
    "align": {
        "beforeColon": true,
        "afterColon": true,
        "on": "colon"
    }
}]*/

var obj = {
    "myObjectFunction": function() {
        // Do something
        //
    }, // These are two separate groups, so no alignment between `myObjectFuction` and `one`
    "one"   : 1,
    "seven" : 7 // `one` and `seven` are in their own group, and therefore aligned
}

singleLine and multiLine

Examples of correct code for this rule with sample { "singleLine": { }, "multiLine": { } } options:

/*eslint "key-spacing": [2, {
    "singleLine": {
        "beforeColon": false,
        "afterColon": true
    },
    "multiLine": {
        "beforeColon": true,
        "afterColon": true,
        "align": "colon"
    }
}]*/
var obj = { one: 1, "two": 2, three: 3 };
var obj2 = {
    "two" : 2,
    three : 3
};

When Not To Use It

If you have another convention for property spacing that might not be consistent with the available options, or if you want to permit multiple styles concurrently you can safely disable this rule. Source: http://eslint.org/docs/rules/