eslint/docs/rules/no-useless-computed-key.md

   1 # Disallow unnecessary computed property keys in objects and classes (no-useless-computed-key)
   2
   3 It's unnecessary to use computed properties with literals such as:
   4
   5 ```js
   6 var foo = {["a"]: "b"};
   7 ```
   8
   9 The code can be rewritten as:
  10
  11 ```js
  12 var foo = {"a": "b"};
  13 ```
  14
  15 ## Rule Details
  16
  17 This rule disallows unnecessary usage of computed property keys.
  18
  19 Examples of **incorrect** code for this rule:
  20
  21 ```js
  22 /*eslint no-useless-computed-key: "error"*/
  23 /*eslint-env es6*/
  24
  25 var a = { ['0']: 0 };
  26 var a = { ['0+1,234']: 0 };
  27 var a = { [0]: 0 };
  28 var a = { ['x']: 0 };
  29 var a = { ['x']() {} };
  30 ```
  31
  32 Examples of **correct** code for this rule:
  33
  34 ```js
  35 /*eslint no-useless-computed-key: "error"*/
  36
  37 var c = { 'a': 0 };
  38 var c = { 0: 0 };
  39 var a = { x() {} };
  40 var c = { a: 0 };
  41 var c = { '0+1,234': 0 };
  42 ```
  43
  44 ## Options
  45
  46 This rule has an object option:
  47
  48 * `enforceForClassMembers` set to `true` additionally applies this rule to class members (Default `false`).
  49
  50 ### enforceForClassMembers
  51
  52 By default, this rule does not check class declarations and class expressions,
  53 as the default value for `enforceForClassMembers` is `false`.
  54
  55 When `enforceForClassMembers` is set to `true`, the rule will also disallow unnecessary computed
  56 keys inside of class methods, getters and setters.
  57
  58 Examples of **incorrect** code for `{ "enforceForClassMembers": true }`:
  59
  60 ```js
  61 /*eslint no-useless-computed-key: ["error", { "enforceForClassMembers": true }]*/
  62
  63 class Foo {
  64     [0]() {}
  65     ['a']() {}
  66     get ['b']() {}
  67     set ['c'](value) {}
  68
  69     static ['a']() {}
  70 }
  71 ```
  72
  73 ## When Not To Use It
  74
  75 If you don't want to be notified about unnecessary computed property keys, you can safely disable this rule.