Function processReplaceRightCell
has a Cognitive Complexity of 45 (exceeds 5 allowed). Consider refactoring. Open
ManageIQ.explorer.processReplaceRightCell = function(data) {
/* variables for the expression editor */
if (_.isObject(data.expEditor)) {
if (_.isObject(data.expEditor.first)) {
if (!_.isUndefined(data.expEditor.first.type)) {
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Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Function processReplaceRightCell
has 116 lines of code (exceeds 25 allowed). Consider refactoring. Open
ManageIQ.explorer.processReplaceRightCell = function(data) {
/* variables for the expression editor */
if (_.isObject(data.expEditor)) {
if (_.isObject(data.expEditor.first)) {
if (!_.isUndefined(data.expEditor.first.type)) {
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Function setVisibility
has a Cognitive Complexity of 9 (exceeds 5 allowed). Consider refactoring. Open
ManageIQ.explorer.setVisibility = function(data) {
if (_.isObject(data.setVisibility)) {
_.forEach(data.setVisibility, function(visible, element) {
if ( miqDomElementExists(element) ) {
if ( visible ) {
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Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Function updateElement
has a Cognitive Complexity of 6 (exceeds 5 allowed). Consider refactoring. Open
ManageIQ.explorer.updateElement = function(element, options) {
if (_.isString(options.legend)) {
$('#' + element).html(options.legend);
} else if (_.isString(options.title)) {
$('#' + element).attr( {'title': options.title});
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Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Unexpected function expression. Open
_.forEach(data.replacePartials, function(content, element) {
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Require using arrow functions for callbacks (prefer-arrow-callback)
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Rule Details
This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
Instances where an arrow function would not produce identical results will be ignored.
The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
/* eslint-env es6 */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
Options
Access further control over this rule's behavior via an options object.
Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
By default { "allowNamedFunctions": false }
, this boolean
option prohibits using named functions as callbacks or function arguments.
Changing this value to true
will reverse this option's behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true }
will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
By default { "allowUnboundThis": true }
, this boolean
option allows function expressions containing this
to be used as callbacks, as long as the function in question has not been explicitly bound.
When set to false
this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false }
will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
/* eslint-env es6 */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
In environments that have not yet adopted ES6 language features (ES3/5).
In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
Further Reading
Unexpected string concatenation. Open
console.error('replacePartials: #' + element + ' does not exist in the DOM');
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
var element = $('#' + data.focus);
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
A space is required before '}'. Open
ManageIQ.redux.store.dispatch({type: 'FormButtons.reset'});
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enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
Unexpected var, use let or const instead. Open
var element = $('#' + data.focus);
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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/
Unexpected string concatenation. Open
$('#' + element).hide();
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- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
A space is required after '{'. Open
$('#' + element).attr( {'title': options.title});
- Read upRead up
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- Exclude checks
enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
There should be no spaces inside this paren. Open
if ( visible ) {
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Disallow or enforce spaces inside of parentheses (space-in-parens)
Some style guides require or disallow spaces inside of parentheses:
foo( 'bar' );
var x = ( 1 + 2 ) * 3;
foo('bar');
var x = (1 + 2) * 3;
Rule Details
This rule will enforce consistency of spacing directly inside of parentheses, by disallowing or requiring one or more spaces to the right of (
and to the left of )
. In either case, ()
will still be allowed.
Options
There are two options for this rule:
-
"never"
(default) enforces zero spaces inside of parentheses -
"always"
enforces a space inside of parentheses
Depending on your coding conventions, you can choose either option by specifying it in your configuration:
"space-in-parens": ["error", "always"]
"never"
Examples of incorrect code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo( 'bar');
foo('bar' );
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Examples of correct code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo();
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
"always"
Examples of incorrect code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo( 'bar');
foo('bar' );
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
Examples of correct code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo();
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Exceptions
An object literal may be used as a third array item to specify exceptions, with the key "exceptions"
and an array as the value. These exceptions work in the context of the first option. That is, if "always"
is set to enforce spacing, then any "exception" will disallow spacing. Conversely, if "never"
is set to disallow spacing, then any "exception" will enforce spacing.
The following exceptions are available: ["{}", "[]", "()", "empty"]
.
Examples of incorrect code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo(1, {bar: 'baz'});
Examples of correct code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo(1, {bar: 'baz'} );
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo( 1, {bar: 'baz'} );
Examples of correct code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo( 1, {bar: 'baz'});
Examples of incorrect code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1);
Examples of correct code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1 );
Examples of incorrect code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo((1 + 2));
foo((1 + 2), 1);
Examples of correct code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo( (1 + 2) );
foo( (1 + 2), 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo( ( 1 + 2 ) );
foo( ( 1 + 2 ), 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo(( 1 + 2 ));
foo(( 1 + 2 ), 1 );
The "empty"
exception concerns empty parentheses, and works the same way as the other exceptions, inverting the first option.
Example of incorrect code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo();
Example of correct code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo( );
Example of incorrect code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo( );
Example of correct code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo();
You can include multiple entries in the "exceptions"
array.
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar( {bar:'baz'} );
baz( 1, [1,2] );
foo( {bar: 'baz'}, [1, 2] );
Examples of correct code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar({bar:'baz'});
baz( 1, [1,2]);
foo({bar: 'baz'}, [1, 2]);
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between parentheses.
Related Rules
- [space-in-brackets](space-in-brackets.md) (deprecated) Source: http://eslint.org/docs/rules/
All 'var' declarations must be at the top of the function scope. Open
var element = $('#' + data.focus);
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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
Unexpected string concatenation. Open
$('#' + element).html(content);
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
$('#' + element).attr( {'title': options.title});
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
A space is required before '}'. Open
sendDataWithRx({reloadTrees: data.reloadTrees});
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enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
A space is required after '{'. Open
sendDataWithRx({reloadTrees: data.reloadTrees});
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enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
console.error('updatePartials: #' + element + ' does not exist in the DOM');
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
$('#' + element).html(content);
- Read upRead up
- Create a ticketCreate a ticket
- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
There should be no spaces inside this paren. Open
if ( miqDomElementExists(element) ) {
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Disallow or enforce spaces inside of parentheses (space-in-parens)
Some style guides require or disallow spaces inside of parentheses:
foo( 'bar' );
var x = ( 1 + 2 ) * 3;
foo('bar');
var x = (1 + 2) * 3;
Rule Details
This rule will enforce consistency of spacing directly inside of parentheses, by disallowing or requiring one or more spaces to the right of (
and to the left of )
. In either case, ()
will still be allowed.
Options
There are two options for this rule:
-
"never"
(default) enforces zero spaces inside of parentheses -
"always"
enforces a space inside of parentheses
Depending on your coding conventions, you can choose either option by specifying it in your configuration:
"space-in-parens": ["error", "always"]
"never"
Examples of incorrect code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo( 'bar');
foo('bar' );
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Examples of correct code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo();
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
"always"
Examples of incorrect code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo( 'bar');
foo('bar' );
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
Examples of correct code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo();
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Exceptions
An object literal may be used as a third array item to specify exceptions, with the key "exceptions"
and an array as the value. These exceptions work in the context of the first option. That is, if "always"
is set to enforce spacing, then any "exception" will disallow spacing. Conversely, if "never"
is set to disallow spacing, then any "exception" will enforce spacing.
The following exceptions are available: ["{}", "[]", "()", "empty"]
.
Examples of incorrect code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo(1, {bar: 'baz'});
Examples of correct code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo(1, {bar: 'baz'} );
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo( 1, {bar: 'baz'} );
Examples of correct code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo( 1, {bar: 'baz'});
Examples of incorrect code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1);
Examples of correct code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1 );
Examples of incorrect code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo((1 + 2));
foo((1 + 2), 1);
Examples of correct code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo( (1 + 2) );
foo( (1 + 2), 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo( ( 1 + 2 ) );
foo( ( 1 + 2 ), 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo(( 1 + 2 ));
foo(( 1 + 2 ), 1 );
The "empty"
exception concerns empty parentheses, and works the same way as the other exceptions, inverting the first option.
Example of incorrect code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo();
Example of correct code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo( );
Example of incorrect code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo( );
Example of correct code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo();
You can include multiple entries in the "exceptions"
array.
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar( {bar:'baz'} );
baz( 1, [1,2] );
foo( {bar: 'baz'}, [1, 2] );
Examples of correct code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar({bar:'baz'});
baz( 1, [1,2]);
foo({bar: 'baz'}, [1, 2]);
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between parentheses.
Related Rules
- [space-in-brackets](space-in-brackets.md) (deprecated) Source: http://eslint.org/docs/rules/
Unexpected function expression. Open
_.forEach(data.updateElements, function(options, element) {
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Require using arrow functions for callbacks (prefer-arrow-callback)
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Rule Details
This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
Instances where an arrow function would not produce identical results will be ignored.
The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
/* eslint-env es6 */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
Options
Access further control over this rule's behavior via an options object.
Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
By default { "allowNamedFunctions": false }
, this boolean
option prohibits using named functions as callbacks or function arguments.
Changing this value to true
will reverse this option's behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true }
will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
By default { "allowUnboundThis": true }
, this boolean
option allows function expressions containing this
to be used as callbacks, as long as the function in question has not been explicitly bound.
When set to false
this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false }
will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
/* eslint-env es6 */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
In environments that have not yet adopted ES6 language features (ES3/5).
In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
Further Reading
Unexpected string concatenation. Open
$('#' + element).html(options.legend);
- Read upRead up
- Create a ticketCreate a ticket
- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
There should be no spaces inside this paren. Open
$('#' + element).attr( {'title': options.title});
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Disallow or enforce spaces inside of parentheses (space-in-parens)
Some style guides require or disallow spaces inside of parentheses:
foo( 'bar' );
var x = ( 1 + 2 ) * 3;
foo('bar');
var x = (1 + 2) * 3;
Rule Details
This rule will enforce consistency of spacing directly inside of parentheses, by disallowing or requiring one or more spaces to the right of (
and to the left of )
. In either case, ()
will still be allowed.
Options
There are two options for this rule:
-
"never"
(default) enforces zero spaces inside of parentheses -
"always"
enforces a space inside of parentheses
Depending on your coding conventions, you can choose either option by specifying it in your configuration:
"space-in-parens": ["error", "always"]
"never"
Examples of incorrect code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo( 'bar');
foo('bar' );
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Examples of correct code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo();
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
"always"
Examples of incorrect code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo( 'bar');
foo('bar' );
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
Examples of correct code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo();
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Exceptions
An object literal may be used as a third array item to specify exceptions, with the key "exceptions"
and an array as the value. These exceptions work in the context of the first option. That is, if "always"
is set to enforce spacing, then any "exception" will disallow spacing. Conversely, if "never"
is set to disallow spacing, then any "exception" will enforce spacing.
The following exceptions are available: ["{}", "[]", "()", "empty"]
.
Examples of incorrect code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo(1, {bar: 'baz'});
Examples of correct code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo(1, {bar: 'baz'} );
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo( 1, {bar: 'baz'} );
Examples of correct code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo( 1, {bar: 'baz'});
Examples of incorrect code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1);
Examples of correct code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1 );
Examples of incorrect code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo((1 + 2));
foo((1 + 2), 1);
Examples of correct code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo( (1 + 2) );
foo( (1 + 2), 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo( ( 1 + 2 ) );
foo( ( 1 + 2 ), 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo(( 1 + 2 ));
foo(( 1 + 2 ), 1 );
The "empty"
exception concerns empty parentheses, and works the same way as the other exceptions, inverting the first option.
Example of incorrect code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo();
Example of correct code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo( );
Example of incorrect code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo( );
Example of correct code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo();
You can include multiple entries in the "exceptions"
array.
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar( {bar:'baz'} );
baz( 1, [1,2] );
foo( {bar: 'baz'}, [1, 2] );
Examples of correct code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar({bar:'baz'});
baz( 1, [1,2]);
foo({bar: 'baz'}, [1, 2]);
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between parentheses.
Related Rules
- [space-in-brackets](space-in-brackets.md) (deprecated) Source: http://eslint.org/docs/rules/
Unnecessarily quoted property 'title' found. Open
$('#' + element).attr( {'title': options.title});
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require quotes around object literal property names (quote-props)
Object literal property names can be defined in two ways: using literals or using strings. For example, these two objects are equivalent:
var object1 = {
property: true
};
var object2 = {
"property": true
};
In many cases, it doesn't matter if you choose to use an identifier instead of a string or vice-versa. Even so, you might decide to enforce a consistent style in your code.
There are, however, some occasions when you must use quotes:
- If you are using an ECMAScript 3 JavaScript engine (such as IE8) and you want to use a keyword (such as
if
) as a property name. This restriction was removed in ECMAScript 5. - You want to use a non-identifier character in your property name, such as having a property with a space like
"one two"
.
Another example where quotes do matter is when using numeric literals as property keys:
var object = {
1e2: 1,
100: 2
};
This may look alright at first sight, but this code in fact throws a syntax error in ECMAScript 5 strict mode. This happens because 1e2
and 100
are coerced into strings before getting used as the property name. Both String(1e2)
and String(100)
happen to be equal to "100"
, which causes the "Duplicate data property in object literal not allowed in strict mode" error. Issues like that can be tricky to debug, so some prefer to require quotes around all property names.
Rule Details
This rule requires quotes around object literal property names.
Options
This rule has two options, a string option and an object option.
String option:
-
"always"
(default) requires quotes around all object literal property names -
"as-needed"
disallows quotes around object literal property names that are not strictly required -
"consistent"
enforces a consistent quote style; in a given object, either all of the properties should be quoted, or none of the properties should be quoted -
"consistent-as-needed"
requires quotes around all object literal property names if any name strictly requires quotes, otherwise disallows quotes around object property names
Object option:
-
"keywords": true
requires quotes around language keywords used as object property names (only applies when usingas-needed
orconsistent-as-needed
) -
"unnecessary": true
(default) disallows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"unnecessary": false
allows quotes around object literal property names that are not strictly required (only applies when usingas-needed
) -
"numbers": true
requires quotes around numbers used as object property names (only applies when usingas-needed
)
always
Examples of incorrect code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
var object = {
foo: "bar",
baz: 42,
"qux-lorem": true
};
Examples of correct code for this rule with the default "always"
option:
/*eslint quote-props: ["error", "always"]*/
/*eslint-env es6*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
as-needed
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
var object = {
"a": 0,
"0": 0,
"true": 0,
"null": 0
};
Examples of correct code for this rule with the "as-needed"
option:
/*eslint quote-props: ["error", "as-needed"]*/
/*eslint-env es6*/
var object1 = {
"a-b": 0,
"0x0": 0,
"1e2": 0
};
var object2 = {
foo: 'bar',
baz: 42,
true: 0,
0: 0,
'qux-lorem': true
};
var object3 = {
foo() {
return;
}
};
consistent
Examples of incorrect code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
baz: 42
};
Examples of correct code for this rule with the "consistent"
option:
/*eslint quote-props: ["error", "consistent"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
var object3 = {
foo: 'bar',
baz: 42
};
consistent-as-needed
Examples of incorrect code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
foo: "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
'foo': 'bar',
'baz': 42
};
Examples of correct code for this rule with the "consistent-as-needed"
option:
/*eslint quote-props: ["error", "consistent-as-needed"]*/
var object1 = {
"foo": "bar",
"baz": 42,
"qux-lorem": true
};
var object2 = {
foo: 'bar',
baz: 42
};
keywords
Examples of additional incorrect code for this rule with the "as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true }]*/
var x = {
while: 1,
volatile: "foo"
};
Examples of additional incorrect code for this rule with the "consistent-as-needed", { "keywords": true }
options:
/*eslint quote-props: ["error", "consistent-as-needed", { "keywords": true }]*/
var x = {
"prop": 1,
"bar": "foo"
};
unnecessary
Examples of additional correct code for this rule with the "as-needed", { "unnecessary": false }
options:
/*eslint quote-props: ["error", "as-needed", { "keywords": true, "unnecessary": false }]*/
var x = {
"while": 1,
"foo": "bar" // Would normally have caused a warning
};
numbers
Examples of additional incorrect code for this rule with the "as-needed", { "numbers": true }
options:
/*eslint quote-props: ["error", "as-needed", { "numbers": true }]*/
var x = {
100: 1
}
When Not To Use It
If you don't care if property names are consistently wrapped in quotes or not, and you don't target legacy ES3 environments, turn this rule off.
Further Reading
Unexpected string concatenation. Open
$('#' + element).addClass(options.class);
- Read upRead up
- Create a ticketCreate a ticket
- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
A space is required after '{'. Open
ManageIQ.redux.store.dispatch({type: 'FormButtons.reset'});
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enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
miqAccordionSwap('#accordion .panel-collapse.collapse.in', '#' + data.accordionSwap + '_accord');
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected var, use let or const instead. Open
var delNode = miqTreeFindNodeByKey(data.deleteNode.activeTree, data.deleteNode.node);
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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/
Unexpected string concatenation. Open
$('#' + element).removeClass(options.class);
- Read upRead up
- Create a ticketCreate a ticket
- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
$('#' + element).replaceWith(content);
- Read upRead up
- Create a ticketCreate a ticket
- Exclude checks
Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected function expression. Open
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Require using arrow functions for callbacks (prefer-arrow-callback)
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Rule Details
This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
Instances where an arrow function would not produce identical results will be ignored.
The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
/* eslint-env es6 */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
Options
Access further control over this rule's behavior via an options object.
Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
By default { "allowNamedFunctions": false }
, this boolean
option prohibits using named functions as callbacks or function arguments.
Changing this value to true
will reverse this option's behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true }
will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
By default { "allowUnboundThis": true }
, this boolean
option allows function expressions containing this
to be used as callbacks, as long as the function in question has not been explicitly bound.
When set to false
this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false }
will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
/* eslint-env es6 */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
In environments that have not yet adopted ES6 language features (ES3/5).
In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
Further Reading
There should be no spaces inside this paren. Open
if ( visible ) {
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Disallow or enforce spaces inside of parentheses (space-in-parens)
Some style guides require or disallow spaces inside of parentheses:
foo( 'bar' );
var x = ( 1 + 2 ) * 3;
foo('bar');
var x = (1 + 2) * 3;
Rule Details
This rule will enforce consistency of spacing directly inside of parentheses, by disallowing or requiring one or more spaces to the right of (
and to the left of )
. In either case, ()
will still be allowed.
Options
There are two options for this rule:
-
"never"
(default) enforces zero spaces inside of parentheses -
"always"
enforces a space inside of parentheses
Depending on your coding conventions, you can choose either option by specifying it in your configuration:
"space-in-parens": ["error", "always"]
"never"
Examples of incorrect code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo( 'bar');
foo('bar' );
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Examples of correct code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo();
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
"always"
Examples of incorrect code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo( 'bar');
foo('bar' );
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
Examples of correct code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo();
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Exceptions
An object literal may be used as a third array item to specify exceptions, with the key "exceptions"
and an array as the value. These exceptions work in the context of the first option. That is, if "always"
is set to enforce spacing, then any "exception" will disallow spacing. Conversely, if "never"
is set to disallow spacing, then any "exception" will enforce spacing.
The following exceptions are available: ["{}", "[]", "()", "empty"]
.
Examples of incorrect code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo(1, {bar: 'baz'});
Examples of correct code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo(1, {bar: 'baz'} );
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo( 1, {bar: 'baz'} );
Examples of correct code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo( 1, {bar: 'baz'});
Examples of incorrect code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1);
Examples of correct code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1 );
Examples of incorrect code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo((1 + 2));
foo((1 + 2), 1);
Examples of correct code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo( (1 + 2) );
foo( (1 + 2), 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo( ( 1 + 2 ) );
foo( ( 1 + 2 ), 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo(( 1 + 2 ));
foo(( 1 + 2 ), 1 );
The "empty"
exception concerns empty parentheses, and works the same way as the other exceptions, inverting the first option.
Example of incorrect code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo();
Example of correct code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo( );
Example of incorrect code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo( );
Example of correct code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo();
You can include multiple entries in the "exceptions"
array.
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar( {bar:'baz'} );
baz( 1, [1,2] );
foo( {bar: 'baz'}, [1, 2] );
Examples of correct code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar({bar:'baz'});
baz( 1, [1,2]);
foo({bar: 'baz'}, [1, 2]);
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between parentheses.
Related Rules
- [space-in-brackets](space-in-brackets.md) (deprecated) Source: http://eslint.org/docs/rules/
Unexpected string concatenation. Open
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Suggest using template literals instead of string concatenation. (prefer-template)
In ES2015 (ES6), we can use template literals instead of string concatenation.
var str = "Hello, " + name + "!";
/*eslint-env es6*/
var str = `Hello, ${name}!`;
Rule Details
This rule is aimed to flag usage of +
operators with strings.
Examples
Examples of incorrect code for this rule:
/*eslint prefer-template: "error"*/
var str = "Hello, " + name + "!";
var str = "Time: " + (12 * 60 * 60 * 1000);
Examples of correct code for this rule:
/*eslint prefer-template: "error"*/
/*eslint-env es6*/
var str = "Hello World!";
var str = `Hello, ${name}!`;
var str = `Time: ${12 * 60 * 60 * 1000}`;
// This is reported by `no-useless-concat`.
var str = "Hello, " + "World!";
When Not To Use It
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about string concatenation, you can safely disable this rule.
Related Rules
- [no-useless-concat](no-useless-concat.md)
- [quotes](quotes.md) Source: http://eslint.org/docs/rules/
Unexpected function expression. Open
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Require using arrow functions for callbacks (prefer-arrow-callback)
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Rule Details
This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
Instances where an arrow function would not produce identical results will be ignored.
The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
/* eslint-env es6 */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
Options
Access further control over this rule's behavior via an options object.
Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
By default { "allowNamedFunctions": false }
, this boolean
option prohibits using named functions as callbacks or function arguments.
Changing this value to true
will reverse this option's behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true }
will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
By default { "allowUnboundThis": true }
, this boolean
option allows function expressions containing this
to be used as callbacks, as long as the function in question has not been explicitly bound.
When set to false
this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false }
will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
/* eslint-env es6 */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
In environments that have not yet adopted ES6 language features (ES3/5).
In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
Further Reading
Unexpected function expression. Open
_.forEach(data.updatePartials, function(content, element) {
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Require using arrow functions for callbacks (prefer-arrow-callback)
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Rule Details
This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
Instances where an arrow function would not produce identical results will be ignored.
The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
/* eslint-env es6 */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
Options
Access further control over this rule's behavior via an options object.
Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
By default { "allowNamedFunctions": false }
, this boolean
option prohibits using named functions as callbacks or function arguments.
Changing this value to true
will reverse this option's behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true }
will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
By default { "allowUnboundThis": true }
, this boolean
option allows function expressions containing this
to be used as callbacks, as long as the function in question has not been explicitly bound.
When set to false
this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false }
will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
/* eslint-env es6 */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(itm) { return this.doSomething(itm); }, someObject);
When Not To Use It
In environments that have not yet adopted ES6 language features (ES3/5).
In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
Further Reading
There should be no spaces inside this paren. Open
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Disallow or enforce spaces inside of parentheses (space-in-parens)
Some style guides require or disallow spaces inside of parentheses:
foo( 'bar' );
var x = ( 1 + 2 ) * 3;
foo('bar');
var x = (1 + 2) * 3;
Rule Details
This rule will enforce consistency of spacing directly inside of parentheses, by disallowing or requiring one or more spaces to the right of (
and to the left of )
. In either case, ()
will still be allowed.
Options
There are two options for this rule:
-
"never"
(default) enforces zero spaces inside of parentheses -
"always"
enforces a space inside of parentheses
Depending on your coding conventions, you can choose either option by specifying it in your configuration:
"space-in-parens": ["error", "always"]
"never"
Examples of incorrect code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo( 'bar');
foo('bar' );
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Examples of correct code for this rule with the default "never"
option:
/*eslint space-in-parens: ["error", "never"]*/
foo();
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
"always"
Examples of incorrect code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo( 'bar');
foo('bar' );
foo('bar');
var foo = (1 + 2) * 3;
(function () { return 'bar'; }());
Examples of correct code for this rule with the "always"
option:
/*eslint space-in-parens: ["error", "always"]*/
foo();
foo( 'bar' );
var foo = ( 1 + 2 ) * 3;
( function () { return 'bar'; }() );
Exceptions
An object literal may be used as a third array item to specify exceptions, with the key "exceptions"
and an array as the value. These exceptions work in the context of the first option. That is, if "always"
is set to enforce spacing, then any "exception" will disallow spacing. Conversely, if "never"
is set to disallow spacing, then any "exception" will enforce spacing.
The following exceptions are available: ["{}", "[]", "()", "empty"]
.
Examples of incorrect code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo(1, {bar: 'baz'});
Examples of correct code for this rule with the "never", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo(1, {bar: 'baz'} );
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo( {bar: 'baz'} );
foo( 1, {bar: 'baz'} );
Examples of correct code for this rule with the "always", { "exceptions": ["{}"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}"] }]*/
foo({bar: 'baz'});
foo( 1, {bar: 'baz'});
Examples of incorrect code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1);
Examples of correct code for this rule with the "never", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo( [bar, baz] );
foo( [bar, baz], 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["[]"] }
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["[]"] }]*/
foo([bar, baz]);
foo([bar, baz], 1 );
Examples of incorrect code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo((1 + 2));
foo((1 + 2), 1);
Examples of correct code for this rule with the "never", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["()"] }]*/
foo( (1 + 2) );
foo( (1 + 2), 1);
Examples of incorrect code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo( ( 1 + 2 ) );
foo( ( 1 + 2 ), 1 );
Examples of correct code for this rule with the "always", { "exceptions": ["()"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["()"] }]*/
foo(( 1 + 2 ));
foo(( 1 + 2 ), 1 );
The "empty"
exception concerns empty parentheses, and works the same way as the other exceptions, inverting the first option.
Example of incorrect code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo();
Example of correct code for this rule with the "never", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "never", { "exceptions": ["empty"] }]*/
foo( );
Example of incorrect code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo( );
Example of correct code for this rule with the "always", { "exceptions": ["empty"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["empty"] }]*/
foo();
You can include multiple entries in the "exceptions"
array.
Examples of incorrect code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar( {bar:'baz'} );
baz( 1, [1,2] );
foo( {bar: 'baz'}, [1, 2] );
Examples of correct code for this rule with the "always", { "exceptions": ["{}", "[]"] }]
option:
/*eslint space-in-parens: ["error", "always", { "exceptions": ["{}", "[]"] }]*/
bar({bar:'baz'});
baz( 1, [1,2]);
foo({bar: 'baz'}, [1, 2]);
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between parentheses.
Related Rules
- [space-in-brackets](space-in-brackets.md) (deprecated) Source: http://eslint.org/docs/rules/
A space is required before '}'. Open
$('#' + element).attr( {'title': options.title});
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enforce consistent spacing inside braces (object-curly-spacing)
While formatting preferences are very personal, a number of style guides require or disallow spaces between curly braces in the following situations:
// simple object literals
var obj = { foo: "bar" };
// nested object literals
var obj = { foo: { zoo: "bar" } };
// destructuring assignment (EcmaScript 6)
var { x, y } = y;
// import/export declarations (EcmaScript 6)
import { foo } from "bar";
export { foo };
Rule Details
This rule enforces consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers.
Options
This rule has two options, a string option and an object option.
String option:
-
"never"
(default) disallows spacing inside of braces -
"always"
requires spacing inside of braces (except{}
)
Object option:
-
"arraysInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set tonever
) -
"arraysInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an array element (applies when the first option is set toalways
) -
"objectsInObjects": true
requires spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set tonever
) -
"objectsInObjects": false
disallows spacing inside of braces of objects beginning and/or ending with an object element (applies when the first option is set toalways
)
never
Examples of incorrect code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = { 'foo': 'bar' };
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux'}, bar};
var {x } = y;
import { foo } from 'bar';
Examples of correct code for this rule with the default "never"
option:
/*eslint object-curly-spacing: ["error", "never"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': {'bar': 'baz'}, 'qux': 'quxx'};
var obj = {
'foo': 'bar'
};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var obj = {};
var {x} = y;
import {foo} from 'bar';
always
Examples of incorrect code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {'foo': 'bar'};
var obj = {'foo': 'bar' };
var obj = { baz: {'foo': 'qux'}, bar};
var obj = {baz: { 'foo': 'qux' }, bar};
var obj = {'foo': 'bar'
};
var obj = {
'foo':'bar'};
var {x} = y;
import {foo } from 'bar';
Examples of correct code for this rule with the "always"
option:
/*eslint object-curly-spacing: ["error", "always"]*/
var obj = {};
var obj = { 'foo': 'bar' };
var obj = { 'foo': { 'bar': 'baz' }, 'qux': 'quxx' };
var obj = {
'foo': 'bar'
};
var { x } = y;
import { foo } from 'bar';
arraysInObjects
Examples of additional correct code for this rule with the "never", { "arraysInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "arraysInObjects": true }]*/
var obj = {"foo": [ 1, 2 ] };
var obj = {"foo": [ "baz", "bar" ] };
Examples of additional correct code for this rule with the "always", { "arraysInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "arraysInObjects": false }]*/
var obj = { "foo": [ 1, 2 ]};
var obj = { "foo": [ "baz", "bar" ]};
objectsInObjects
Examples of additional correct code for this rule with the "never", { "objectsInObjects": true }
options:
/*eslint object-curly-spacing: ["error", "never", { "objectsInObjects": true }]*/
var obj = {"foo": {"baz": 1, "bar": 2} };
Examples of additional correct code for this rule with the "always", { "objectsInObjects": false }
options:
/*eslint object-curly-spacing: ["error", "always", { "objectsInObjects": false }]*/
var obj = { "foo": { "baz": 1, "bar": 2 }};
When Not To Use It
You can turn this rule off if you are not concerned with the consistency of spacing between curly braces.
Related Rules
- [array-bracket-spacing](array-bracket-spacing.md)
- [comma-spacing](comma-spacing.md)
- [computed-property-spacing](computed-property-spacing.md)
- [space-in-parens](space-in-parens.md) Source: http://eslint.org/docs/rules/
All 'var' declarations must be at the top of the function scope. Open
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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
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Disallow Undeclared Variables (no-undef)
This rule can help you locate potential ReferenceErrors resulting from misspellings of variable and parameter names, or accidental implicit globals (for example, from forgetting the var
keyword in a for
loop initializer).
Rule Details
Any reference to an undeclared variable causes a warning, unless the variable is explicitly mentioned in a /*global ...*/
comment, or specified in the globals
key in the configuration file. A common use case for these is if you intentionally use globals that are defined elsewhere (e.g. in a script sourced from HTML).
Examples of incorrect code for this rule:
/*eslint no-undef: "error"*/
var a = someFunction();
b = 10;
Examples of correct code for this rule with global
declaration:
/*global someFunction b:true*/
/*eslint no-undef: "error"*/
var a = someFunction();
b = 10;
The b:true
syntax in /*global */
indicates that assignment to b
is correct.
Examples of incorrect code for this rule with global
declaration:
/*global b*/
/*eslint no-undef: "error"*/
b = 10;
By default, variables declared in /*global */
are read-only, therefore assignment is incorrect.
Options
-
typeof
set to true will warn for variables used inside typeof check (Default false).
typeof
Examples of correct code for the default { "typeof": false }
option:
/*eslint no-undef: "error"*/
if (typeof UndefinedIdentifier === "undefined") {
// do something ...
}
You can use this option if you want to prevent typeof
check on a variable which has not been declared.
Examples of incorrect code for the { "typeof": true }
option:
/*eslint no-undef: ["error", { "typeof": true }] */
if(typeof a === "string"){}
Examples of correct code for the { "typeof": true }
option with global
declaration:
/*global a*/
/*eslint no-undef: ["error", { "typeof": true }] */
if(typeof a === "string"){}
Environments
For convenience, ESLint provides shortcuts that pre-define global variables exposed by popular libraries and runtime environments. This rule supports these environments, as listed in [Specifying Environments](../user-guide/configuring.md#specifying-environments). A few examples are given below.
browser
Examples of correct code for this rule with browser
environment:
/*eslint no-undef: "error"*/
/*eslint-env browser*/
setTimeout(function() {
alert("Hello");
});
Node.js
Examples of correct code for this rule with node
environment:
/*eslint no-undef: "error"*/
/*eslint-env node*/
var fs = require("fs");
module.exports = function() {
console.log(fs);
};
When Not To Use It
If explicit declaration of global variables is not to your taste.
Compatibility
This rule provides compatibility with treatment of global variables in JSHint and JSLint. Source: http://eslint.org/docs/rules/
Multiple spaces found before '='. Open
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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 tofalse
) 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/
Multiple spaces found before '='. Open
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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 tofalse
) 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/
Multiple spaces found before '='. Open
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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 tofalse
) 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/
Multiple spaces found before '='. Open
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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 tofalse
) 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/
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 143.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 143.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
ManageIQ.explorer.replacePartials = function(data) {
if (_.isObject(data.replacePartials)) {
_.forEach(data.replacePartials, function(content, element) {
if (!miqDomElementExists(element)) {
console.error('replacePartials: #' + element + ' does not exist in the DOM');
- Read upRead up
- Create a ticketCreate a ticket
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 114.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
ManageIQ.explorer.updatePartials = function(data) {
if (_.isObject(data.updatePartials)) {
_.forEach(data.updatePartials, function(content, element) {
if (!miqDomElementExists(element)) {
console.error('updatePartials: #' + element + ' does not exist in the DOM');
- Read upRead up
- Create a ticketCreate a ticket
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 114.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76