return nodeValidator.isURL(url, options) ||

Close

enforce consistent linebreak style for operators (operator-linebreak)

When a statement is too long to fit on a single line, line breaks are generally inserted next to the operators separating expressions. The first style coming to mind would be to place the operator at the end of the line, following the English punctuation rules.

var fullHeight = borderTop +
                 innerHeight +
                 borderBottom;

Some developers find that placing operators at the beginning of the line makes the code more readable.

var fullHeight = borderTop
               + innerHeight
               + borderBottom;

Rule Details

This rule enforces a consistent linebreak style for operators.

Options

This rule has one option, which can be a string option or an object option.

String option:

• "after" requires linebreaks to be placed after the operator
• "before" requires linebreaks to be placed before the operator
• "none" disallows linebreaks on either side of the operator

Object option:

• "overrides" overrides the global setting for specified operators

The default configuration is "after", { "overrides": { "?": "before", ":": "before" } }

after

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

/*eslint operator-linebreak: ["error", "after"]*/

foo = 1
+
2;

foo = 1
    + 2;

foo
    = 5;

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

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

/*eslint operator-linebreak: ["error", "after"]*/

foo = 1 + 2;

foo = 1 +
      2;

foo =
    5;

if (someCondition ||
    otherCondition) {
}

answer = everything ?
  42 :
  foo;

before

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

/*eslint operator-linebreak: ["error", "before"]*/

foo = 1 +
      2;

foo =
    5;

if (someCondition ||
    otherCondition) {
}

answer = everything ?
  42 :
  foo;

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

/*eslint operator-linebreak: ["error", "before"]*/

foo = 1 + 2;

foo = 1
    + 2;

foo
    = 5;

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

none

Examples of incorrect code for this rule with the "none" option:

/*eslint operator-linebreak: ["error", "none"]*/

foo = 1 +
      2;

foo = 1
    + 2;

if (someCondition ||
    otherCondition) {
}

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

answer = everything ?
  42 :
  foo;

Examples of correct code for this rule with the "none" option:

/*eslint operator-linebreak: ["error", "none"]*/

foo = 1 + 2;

foo = 5;

if (someCondition || otherCondition) {
}

answer = everything ? 42 : foo;

overrides

Examples of additional correct code for this rule with the { "overrides": { "+=": "before" } } option:

/*eslint operator-linebreak: ["error", "after", { "overrides": { "+=": "before" } }]*/

var thing = 'thing';
thing
  += 's';

Examples of additional correct code for this rule with the { "overrides": { "?": "ignore", ":": "ignore" } } option:

/*eslint operator-linebreak: ["error", "after", { "overrides": { "?": "ignore", ":": "ignore" } }]*/

answer = everything ?
  42
  : foo;

answer = everything
  ?
  42
  :
  foo;

When Not To Use It

If your project will not be using a common operator line break style, turn this rule off.

Related Rules

• [comma-style](comma-style.md) Source: http://eslint.org/docs/rules/

      var validUrl = function(url) {

Close

require let or const instead of var (no-var)

ECMAScript 6 allows programmers to create variables with block scope instead of function scope using the let and const keywords. Block scope is common in many other programming languages and helps programmers avoid mistakes such as:

var count = people.length;
var enoughFood = count > sandwiches.length;

if (enoughFood) {
    var count = sandwiches.length; // accidentally overriding the count variable
    console.log("We have " + count + " sandwiches for everyone. Plenty for all!");
}

// our count variable is no longer accurate
console.log("We have " + count + " people and " + sandwiches.length + " sandwiches!");

Rule Details

This rule is aimed at discouraging the use of var and encouraging the use of const or let instead.

Examples

Examples of incorrect code for this rule:

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

var x = "y";
var CONFIG = {};

Examples of correct code for this rule:

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

let x = "y";
const CONFIG = {};

When Not To Use It

In addition to non-ES6 environments, existing JavaScript projects that are beginning to introduce ES6 into their codebase may not want to apply this rule if the cost of migrating from var to let is too costly. Source: http://eslint.org/docs/rules/

    link: function(_scope, _elem, _attrs, ctrl) {

Close

Require Object Literal Shorthand Syntax (object-shorthand)

ECMAScript 6 provides a concise form for defining object literal methods and properties. This syntax can make defining complex object literals much cleaner.

Here are a few common examples using the ES5 syntax:

// properties
var foo = {
    x: x,
    y: y,
    z: z,
};

// methods
var foo = {
    a: function() {},
    b: function() {}
};

Now here are ES6 equivalents:

/*eslint-env es6*/

// properties
var foo = {x, y, z};

// methods
var foo = {
    a() {},
    b() {}
};

Rule Details

This rule enforces the use of the shorthand syntax. This applies to all methods (including generators) defined in object literals and any properties defined where the key name matches name of the assigned variable.

Each of the following properties would warn:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    w: function() {},
    x: function *() {},
    [y]: function() {},
    z: z
};

In that case the expected syntax would have been:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    w() {},
    *x() {},
    [y]() {},
    z
};

This rule does not flag arrow functions inside of object literals. The following will not warn:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    x: (y) => y
};

See Also:

• no-useless-rename which disallows renaming import, export, and destructured assignments to the same name.

Options

The rule takes an option which specifies when it should be applied. It can be set to one of the following values:

• "always" (default) expects that the shorthand will be used whenever possible.
• "methods" ensures the method shorthand is used (also applies to generators).
• "properties" ensures the property shorthand is used (where the key and variable name match).
• "never" ensures that no property or method shorthand is used in any object literal.
• "consistent" ensures that either all shorthand or all long-form will be used in an object literal.
• "consistent-as-needed" ensures that either all shorthand or all long-form will be used in an object literal, but ensures all shorthand whenever possible.

You can set the option in configuration like this:

{
    "object-shorthand": ["error", "always"]
}

Additionally, the rule takes an optional object configuration:

• "avoidQuotes": true indicates that long-form syntax is preferred whenever the object key is a string literal (default: false). Note that this option can only be enabled when the string option is set to "always", "methods", or "properties".
• "ignoreConstructors": true can be used to prevent the rule from reporting errors for constructor functions. (By default, the rule treats constructors the same way as other functions.) Note that this option can only be enabled when the string option is set to "always" or "methods".
• "avoidExplicitReturnArrows": true indicates that methods are preferred over explicit-return arrow functions for function properties. (By default, the rule allows either of these.) Note that this option can only be enabled when the string option is set to "always" or "methods".

avoidQuotes

{
    "object-shorthand": ["error", "always", { "avoidQuotes": true }]
}

Example of incorrect code for this rule with the "always", { "avoidQuotes": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
/*eslint-env es6*/

var foo = {
    "bar-baz"() {}
};

Example of correct code for this rule with the "always", { "avoidQuotes": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
/*eslint-env es6*/

var foo = {
    "bar-baz": function() {},
    "qux": qux
};

ignoreConstructors

{
    "object-shorthand": ["error", "always", { "ignoreConstructors": true }]
}

Example of correct code for this rule with the "always", { "ignoreConstructors": true } option:

/*eslint object-shorthand: ["error", "always", { "ignoreConstructors": true }]*/
/*eslint-env es6*/

var foo = {
    ConstructorFunction: function() {}
};

avoidExplicitReturnArrows

{
    "object-shorthand": ["error", "always", { "avoidExplicitReturnArrows": true }]
}

Example of incorrect code for this rule with the "always", { "avoidExplicitReturnArrows": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
/*eslint-env es6*/

var foo = {
  foo: (bar, baz) => {
    return bar + baz;
  },

  qux: (foobar) => {
    return foobar * 2;
  }
};

Example of correct code for this rule with the "always", { "avoidExplicitReturnArrows": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
/*eslint-env es6*/

var foo = {
  foo(bar, baz) {
    return bar + baz;
  },

  qux: foobar => foobar * 2
};

Example of incorrect code for this rule with the "consistent" option:

/*eslint object-shorthand: [2, "consistent"]*/
/*eslint-env es6*/

var foo = {
    a,
    b: "foo",
};

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

/*eslint object-shorthand: [2, "consistent"]*/
/*eslint-env es6*/

var foo = {
    a: a,
    b: "foo"
};

var bar = {
    a,
    b,
};

Example of incorrect code with the "consistent-as-needed" option, which is very similar to "consistent":

/*eslint object-shorthand: [2, "consistent-as-needed"]*/
/*eslint-env es6*/

var foo = {
    a: a,
    b: b,
};

When Not To Use It

Anyone not yet in an ES6 environment would not want to apply this rule. Others may find the terseness of the shorthand syntax harder to read and may not want to encourage it with this rule.

Further Reading

Object initializer - MDN Source: http://eslint.org/docs/rules/

      var validUrl = function(url) {

Close

Require Variable Declarations to be at the top of their scope (vars-on-top)

The vars-on-top rule generates warnings when variable declarations are not used serially at the top of a function scope or the top of a program. By default variable declarations are always moved (“hoisted”) invisibly to the top of their containing scope by the JavaScript interpreter. This rule forces the programmer to represent that behavior by manually moving the variable declaration to the top of its containing scope.

Rule Details

This rule aims to keep all variable declarations in the leading series of statements. Allowing multiple declarations helps promote maintainability and is thus allowed.

Examples of incorrect code for this rule:

/*eslint vars-on-top: "error"*/

// Variable declarations in a block:
function doSomething() {
    var first;
    if (true) {
        first = true;
    }
    var second;
}

// Variable declaration in for initializer:
function doSomething() {
    for (var i=0; i<10; i++) {}
}

/*eslint vars-on-top: "error"*/

// Variables after other statements:
f();
var a;

Examples of correct code for this rule:

/*eslint vars-on-top: "error"*/

function doSomething() {
    var first;
    var second; //multiple declarations are allowed at the top
    if (true) {
        first = true;
    }
}

function doSomething() {
    var i;
    for (i=0; i<10; i++) {}
}

/*eslint vars-on-top: "error"*/

var a;
f();

/*eslint vars-on-top: "error"*/

// Directives may precede variable declarations.
"use strict";
var a;
f();

// Comments can describe variables.
function doSomething() {
    // this is the first var.
    var first;
    // this is the second var.
    var second
}

Further Reading

• JavaScript Scoping and Hoisting
• var Hoisting
• A criticism of the Single Var Pattern in JavaScript, and a simple alternative
• Multiple var statements in JavaScript, not superfluous Source: http://eslint.org/docs/rules/

      var options = {

Close

require let or const instead of var (no-var)

ECMAScript 6 allows programmers to create variables with block scope instead of function scope using the let and const keywords. Block scope is common in many other programming languages and helps programmers avoid mistakes such as:

var count = people.length;
var enoughFood = count > sandwiches.length;

if (enoughFood) {
    var count = sandwiches.length; // accidentally overriding the count variable
    console.log("We have " + count + " sandwiches for everyone. Plenty for all!");
}

// our count variable is no longer accurate
console.log("We have " + count + " people and " + sandwiches.length + " sandwiches!");

Rule Details

This rule is aimed at discouraging the use of var and encouraging the use of const or let instead.

Examples

Examples of incorrect code for this rule:

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

var x = "y";
var CONFIG = {};

Examples of correct code for this rule:

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

let x = "y";
const CONFIG = {};

When Not To Use It

In addition to non-ES6 environments, existing JavaScript projects that are beginning to introduce ES6 into their codebase may not want to apply this rule if the cost of migrating from var to let is too costly. Source: http://eslint.org/docs/rules/

               url.match(/^file:\/\/\/.+/)       ||

Close

enforce consistent linebreak style for operators (operator-linebreak)

When a statement is too long to fit on a single line, line breaks are generally inserted next to the operators separating expressions. The first style coming to mind would be to place the operator at the end of the line, following the English punctuation rules.

var fullHeight = borderTop +
                 innerHeight +
                 borderBottom;

Some developers find that placing operators at the beginning of the line makes the code more readable.

var fullHeight = borderTop
               + innerHeight
               + borderBottom;

Rule Details

This rule enforces a consistent linebreak style for operators.

Options

This rule has one option, which can be a string option or an object option.

String option:

• "after" requires linebreaks to be placed after the operator
• "before" requires linebreaks to be placed before the operator
• "none" disallows linebreaks on either side of the operator

Object option:

• "overrides" overrides the global setting for specified operators

The default configuration is "after", { "overrides": { "?": "before", ":": "before" } }

after

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

/*eslint operator-linebreak: ["error", "after"]*/

foo = 1
+
2;

foo = 1
    + 2;

foo
    = 5;

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

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

/*eslint operator-linebreak: ["error", "after"]*/

foo = 1 + 2;

foo = 1 +
      2;

foo =
    5;

if (someCondition ||
    otherCondition) {
}

answer = everything ?
  42 :
  foo;

before

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

/*eslint operator-linebreak: ["error", "before"]*/

foo = 1 +
      2;

foo =
    5;

if (someCondition ||
    otherCondition) {
}

answer = everything ?
  42 :
  foo;

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

/*eslint operator-linebreak: ["error", "before"]*/

foo = 1 + 2;

foo = 1
    + 2;

foo
    = 5;

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

none

Examples of incorrect code for this rule with the "none" option:

/*eslint operator-linebreak: ["error", "none"]*/

foo = 1 +
      2;

foo = 1
    + 2;

if (someCondition ||
    otherCondition) {
}

if (someCondition
    || otherCondition) {
}

answer = everything
  ? 42
  : foo;

answer = everything ?
  42 :
  foo;

Examples of correct code for this rule with the "none" option:

/*eslint operator-linebreak: ["error", "none"]*/

foo = 1 + 2;

foo = 5;

if (someCondition || otherCondition) {
}

answer = everything ? 42 : foo;

overrides

Examples of additional correct code for this rule with the { "overrides": { "+=": "before" } } option:

/*eslint operator-linebreak: ["error", "after", { "overrides": { "+=": "before" } }]*/

var thing = 'thing';
thing
  += 's';

Examples of additional correct code for this rule with the { "overrides": { "?": "ignore", ":": "ignore" } } option:

/*eslint operator-linebreak: ["error", "after", { "overrides": { "?": "ignore", ":": "ignore" } }]*/

answer = everything ?
  42
  : foo;

answer = everything
  ?
  42
  :
  foo;

When Not To Use It

If your project will not be using a common operator line break style, turn this rule off.

Related Rules

• [comma-style](comma-style.md) Source: http://eslint.org/docs/rules/

      var options = {

Close

Require Variable Declarations to be at the top of their scope (vars-on-top)

The vars-on-top rule generates warnings when variable declarations are not used serially at the top of a function scope or the top of a program. By default variable declarations are always moved (“hoisted”) invisibly to the top of their containing scope by the JavaScript interpreter. This rule forces the programmer to represent that behavior by manually moving the variable declaration to the top of its containing scope.

Rule Details

This rule aims to keep all variable declarations in the leading series of statements. Allowing multiple declarations helps promote maintainability and is thus allowed.

Examples of incorrect code for this rule:

/*eslint vars-on-top: "error"*/

// Variable declarations in a block:
function doSomething() {
    var first;
    if (true) {
        first = true;
    }
    var second;
}

// Variable declaration in for initializer:
function doSomething() {
    for (var i=0; i<10; i++) {}
}

/*eslint vars-on-top: "error"*/

// Variables after other statements:
f();
var a;

Examples of correct code for this rule:

/*eslint vars-on-top: "error"*/

function doSomething() {
    var first;
    var second; //multiple declarations are allowed at the top
    if (true) {
        first = true;
    }
}

function doSomething() {
    var i;
    for (i=0; i<10; i++) {}
}

/*eslint vars-on-top: "error"*/

var a;
f();

/*eslint vars-on-top: "error"*/

// Directives may precede variable declarations.
"use strict";
var a;
f();

// Comments can describe variables.
function doSomething() {
    // this is the first var.
    var first;
    // this is the second var.
    var second
}

Further Reading

• JavaScript Scoping and Hoisting
• var Hoisting
• A criticism of the Single Var Pattern in JavaScript, and a simple alternative
• Multiple var statements in JavaScript, not superfluous Source: http://eslint.org/docs/rules/

               url.match(/^file:\/\/\/.+/)       ||

Close

Disallow multiple spaces (no-multi-spaces)

Multiple spaces in a row that are not used for indentation are typically mistakes. For example:

if(foo  === "bar") {}

It's hard to tell, but there are two spaces between foo and ===. Multiple spaces such as this are generally frowned upon in favor of single spaces:

if(foo === "bar") {}

Rule Details

This rule aims to disallow multiple whitespace around logical expressions, conditional expressions, declarations, array elements, object properties, sequences and function parameters.

Examples of incorrect code for this rule:

/*eslint no-multi-spaces: "error"*/

var a =  1;

if(foo   === "bar") {}

a <<  b

var arr = [1,  2];

a ?  b: c

Examples of correct code for this rule:

/*eslint no-multi-spaces: "error"*/

var a = 1;

if(foo === "bar") {}

a << b

var arr = [1, 2];

a ? b: c

Options

This rule's configuration consists of an object with the following properties:

• "ignoreEOLComments": true (defaults to false) ignores multiple spaces before comments that occur at the end of lines
• "exceptions": { "Property": true } ("Property" is the only node specified by default) specifies nodes to ignore

ignoreEOLComments

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

/*eslint no-multi-spaces: ["error", { ignoreEOLComments: false }]*/

var x = 5;      // comment
var x = 5;      /* multiline
 * comment
 */

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

/*eslint no-multi-spaces: ["error", { ignoreEOLComments: false }]*/

var x = 5; // comment
var x = 5; /* multiline
 * comment
 */

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

/*eslint no-multi-spaces: ["error", { ignoreEOLComments: true }]*/

var x = 5; // comment
var x = 5;      // comment
var x = 5; /* multiline
 * comment
 */
var x = 5;      /* multiline
 * comment
 */

exceptions

To avoid contradictions with other rules that require multiple spaces, this rule has an exceptions option to ignore certain nodes.

This option is an object that expects property names to be AST node types as defined by ESTree. The easiest way to determine the node types for exceptions is to use the online demo.

Only the Property node type is ignored by default, because for the [key-spacing](key-spacing.md) rule some alignment options require multiple spaces in properties of object literals.

Examples of correct code for the default "exceptions": { "Property": true } option:

/*eslint no-multi-spaces: "error"*/
/*eslint key-spacing: ["error", { align: "value" }]*/

var obj = {
    first:  "first",
    second: "second"
};

Examples of incorrect code for the "exceptions": { "Property": false } option:

/*eslint no-multi-spaces: ["error", { exceptions: { "Property": false } }]*/
/*eslint key-spacing: ["error", { align: "value" }]*/

var obj = {
    first:  "first",
    second: "second"
};

Examples of correct code for the "exceptions": { "BinaryExpression": true } option:

/*eslint no-multi-spaces: ["error", { exceptions: { "BinaryExpression": true } }]*/

var a = 1  *  2;

Examples of correct code for the "exceptions": { "VariableDeclarator": true } option:

/*eslint no-multi-spaces: ["error", { exceptions: { "VariableDeclarator": true } }]*/

var someVar      = 'foo';
var someOtherVar = 'barBaz';

Examples of correct code for the "exceptions": { "ImportDeclaration": true } option:

/*eslint no-multi-spaces: ["error", { exceptions: { "ImportDeclaration": true } }]*/

import mod          from 'mod';
import someOtherMod from 'some-other-mod';

When Not To Use It

If you don't want to check and disallow multiple spaces, then you should turn this rule off.

Related Rules

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