Disallow or enforce spaces inside of computed properties (computed-property-spacing)

The --fix option on the command line can automatically fix some of the problems reported by this rule.

While formatting preferences are very personal, a number of style guides require or disallow spaces between computed properties in the following situations:

/*eslint-env es6*/

var obj = { prop: "value" };
var a = "prop";
var x = obj[a]; // computed property in object member expression

var a = "prop";
var obj = {
  [a]: "value" // computed property key in object literal (ECMAScript 6)
};

Rule Details

This rule enforces consistent spacing inside computed property brackets.

It either requires or disallows spaces between the brackets and the values inside of them. This rule does not apply to brackets that are separated from the adjacent value by a newline.

Options

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

String option:

• "never" (default) disallows spaces inside computed property brackets
• "always" requires one or more spaces inside computed property brackets

Object option:

• "enforceForClassMembers": true additionally applies this rule to class members (default is false)

never

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

/*eslint computed-property-spacing: ["error", "never"]*/
/*eslint-env es6*/

obj[foo ]
obj[ 'foo']
var x = {[ b ]: a}
obj[foo[ bar ]]

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

/*eslint computed-property-spacing: ["error", "never"]*/
/*eslint-env es6*/

obj[foo]
obj['foo']
var x = {[b]: a}
obj[foo[bar]]

always

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

/*eslint computed-property-spacing: ["error", "always"]*/
/*eslint-env es6*/

obj[foo]
var x = {[b]: a}
obj[ foo]
obj['foo' ]
obj[foo[ bar ]]
var x = {[ b]: a}

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

/*eslint computed-property-spacing: ["error", "always"]*/
/*eslint-env es6*/

obj[ foo ]
obj[ 'foo' ]
var x = {[ b ]: a}
obj[ foo[ bar ] ]

enforceForClassMembers

By default, this rule does not check class declarations and class expressions, as the default value for enforceForClassMembers is false.

When enforceForClassMembers is set to true, the rule will also disallow/enforce spaces inside of computed keys of class methods, getters and setters.

Examples of incorrect code for this rule with "never" and { "enforceForClassMembers": true }:

/*eslint computed-property-spacing: ["error", "never", { "enforceForClassMembers": true }]*/
/*eslint-env es6*/

class Foo {
  [a ]() {}
  get [b ]() {}
  set [b ](value) {}
}

const Bar = class {
  [ a](){}
  static [ b]() {}
  static get [ c ]() {}
  static set [ c ](value) {}
}

Examples of correct code for this rule with "never" and { "enforceForClassMembers": true }:

/*eslint computed-property-spacing: ["error", "never", { "enforceForClassMembers": true }]*/
/*eslint-env es6*/

class Foo {
  [a]() {}
  get [b]() {}
  set [b](value) {}
}

const Bar = class {
  [a](){}
  static [b]() {}
  static get [c]() {}
  static set [c](value) {}
}

When Not To Use It

You can turn this rule off if you are not concerned with the consistency of computed properties.

Related Rules

• array-bracket-spacing
• comma-spacing
• space-in-parens

Version

This rule was introduced in ESLint 0.23.0.

Resources

• Rule source
• Documentation source