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array-bracket-spacing

docs/src/rules/array-bracket-spacing.md

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Original Source

A number of style guides require or disallow spaces between array brackets and other tokens. This rule applies to both array literals and destructuring assignments (ECMAScript 6).

js
var arr = [ 'foo', 'bar' ];
var [ x, y ] = z;

var arr = ['foo', 'bar'];
var [x,y] = z;

Rule Details

This rule enforces consistent spacing inside array brackets.

Options

This rule has a string option:

  • "never" (default) disallows spaces inside array brackets
  • "always" requires one or more spaces or newlines inside array brackets

This rule has an object option for exceptions to the "never" option:

  • "singleValue": true requires one or more spaces or newlines inside brackets of array literals that contain a single element
  • "objectsInArrays": true requires one or more spaces or newlines between brackets of array literals and braces of their object literal elements [ { or } ]
  • "arraysInArrays": true requires one or more spaces or newlines between brackets of array literals and brackets of their array literal elements [ [ or ] ]

This rule has an object option for exceptions to the "always" option:

  • "singleValue": false disallows spaces inside brackets of array literals that contain a single element
  • "objectsInArrays": false disallows spaces between brackets of array literals and braces of their object literal elements [{ or }]
  • "arraysInArrays": false disallows spaces between brackets of array literals and brackets of their array literal elements [[ or ]]

This rule has built-in exceptions:

  • "never" (and also the exceptions to the "always" option) allows newlines inside array brackets, because this is a common pattern
  • "always" does not require spaces or newlines in empty array literals []

never

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

:::incorrect

js
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [ 'foo', 'bar' ];
var arr = ['foo', 'bar' ];
var arr = [ ['foo'], 'bar'];
var arr = [[ 'foo' ], 'bar'];
var arr = [ 'foo',
  'bar'
];
var [ x, y ] = z;
var [ x,y ] = z;
var [ x, ...y ] = z;
var [ ,,x, ] = z;

:::

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

:::correct

js
/*eslint array-bracket-spacing: ["error", "never"]*/

var arr = [];
var arr = ['foo', 'bar', 'baz'];
var arr = [['foo'], 'bar', 'baz'];
var arr = [
  'foo',
  'bar',
  'baz'
];
var arr = ['foo',
  'bar'
];
var arr = [
  'foo',
  'bar'];

var [x, y] = z;
var [x,y] = z;
var [x, ...y] = z;
var [,,x,] = z;

:::

always

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

:::incorrect

js
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = ['foo', 'bar'];
var arr = ['foo', 'bar' ];
var arr = [ ['foo'], 'bar' ];
var arr = ['foo',
  'bar'
];
var arr = [
  'foo',
  'bar'];

var [x, y] = z;
var [x,y] = z;
var [x, ...y] = z;
var [,,x,] = z;

:::

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

:::correct

js
/*eslint array-bracket-spacing: ["error", "always"]*/

var arr = [];
var arr = [ 'foo', 'bar', 'baz' ];
var arr = [ [ 'foo' ], 'bar', 'baz' ];
var arr = [ 'foo',
  'bar'
];
var arr = [
  'foo',
  'bar' ];
var arr = [
  'foo',
  'bar',
  'baz'
];

var [ x, y ] = z;
var [ x,y ] = z;
var [ x, ...y ] = z;
var [ ,,x, ] = z;

:::

singleValue

Examples of incorrect code for this rule with the "always", { "singleValue": false } options:

:::incorrect

js
/*eslint array-bracket-spacing: ["error", "always", { "singleValue": false }]*/

var foo = [ 'foo' ];
var foo = [ 'foo'];
var foo = ['foo' ];
var foo = [ 1 ];
var foo = [ 1];
var foo = [1 ];
var foo = [ [ 1, 2 ] ];
var foo = [ { 'foo': 'bar' } ];

:::

Examples of correct code for this rule with the "always", { "singleValue": false } options:

:::correct

js
/*eslint array-bracket-spacing: ["error", "always", { "singleValue": false }]*/

var foo = ['foo'];
var foo = [1];
var foo = [[ 1, 1 ]];
var foo = [{ 'foo': 'bar' }];

:::

objectsInArrays

Examples of incorrect code for this rule with the "always", { "objectsInArrays": false } options:

:::incorrect

js
/*eslint array-bracket-spacing: ["error", "always", { "objectsInArrays": false }]*/

var arr = [ { 'foo': 'bar' } ];
var arr = [ {
  'foo': 'bar'
} ]

:::

Examples of correct code for this rule with the "always", { "objectsInArrays": false } options:

:::correct

js
/*eslint array-bracket-spacing: ["error", "always", { "objectsInArrays": false }]*/

var arr = [{ 'foo': 'bar' }];
var arr = [{
  'foo': 'bar'
}];

:::

arraysInArrays

Examples of incorrect code for this rule with the "always", { "arraysInArrays": false } options:

:::incorrect

js
/*eslint array-bracket-spacing: ["error", "always", { "arraysInArrays": false }]*/

var arr = [ [ 1, 2 ], 2, 3, 4 ];
var arr = [ [ 1, 2 ], 2, [ 3, 4 ] ];

:::

Examples of correct code for this rule with the "always", { "arraysInArrays": false } options:

:::correct

js
/*eslint array-bracket-spacing: ["error", "always", { "arraysInArrays": false }]*/

var arr = [[ 1, 2 ], 2, 3, 4 ];
var arr = [[ 1, 2 ], 2, [ 3, 4 ]];

:::

When Not To Use It

You can turn this rule off if you are not concerned with the consistency of spacing between array brackets.