eslint/docs/src/rules/generator-star.md

   1 ---
   2 title: generator-star
   3 layout: doc
   4 further_reading:
   5 - https://leanpub.com/understandinges6/read/#leanpub-auto-generators
   6 ---
   7
   8 Enforces consistent spacing around the asterisk in generator functions.
   9
  10 (removed) This rule was **removed** in ESLint v1.0 and **replaced** by the [generator-star-spacing](generator-star-spacing) rule.
  11
  12 Generators are a new type of function in ECMAScript 6 that can return multiple values over time.
  13 These special functions are indicated by placing an `*` after the `function` keyword.
  14
  15 Here is an example of a generator function:
  16
  17 ```js
  18 /*eslint-env es6*/
  19
  20 function* generator() {
  21     yield "44";
  22     yield "55";
  23 }
  24 ```
  25
  26 This is also valid:
  27
  28 ```js
  29 /*eslint-env es6*/
  30
  31 function *generator() {
  32     yield "44";
  33     yield "55";
  34 }
  35 ```
  36
  37 This is valid as well:
  38
  39 ```js
  40 /*eslint-env es6*/
  41
  42 function * generator() {
  43     yield "44";
  44     yield "55";
  45 }
  46 ```
  47
  48 To keep a sense of consistency when using generators this rule enforces a single position for the `*`.
  49
  50 ## Rule Details
  51
  52 This rule enforces that the `*` is either placed next to the `function` keyword or the name of the function. The single
  53 option for this rule is a string specifying the placement of the asterisk. For this option you may pass
  54 `"start"`, `"middle"` or `"end"`. The default is `"end"`.
  55
  56 You can set the style in configuration like this:
  57
  58 ```json
  59 "generator-star": ["error", "start"]
  60 ```
  61
  62 When using `"start"` this placement will be enforced:
  63
  64 ```js
  65 /*eslint-env es6*/
  66
  67 function* generator() {
  68 }
  69 ```
  70
  71 When using `"middle"` this placement will be enforced:
  72
  73 ```js
  74 /*eslint-env es6*/
  75
  76 function * generator() {
  77 }
  78 ```
  79
  80 When using `"end"` this placement will be enforced:
  81
  82 ```js
  83 /*eslint-env es6*/
  84
  85 function *generator() {
  86 }
  87 ```
  88
  89 When using the expression syntax `"start"` will be enforced here:
  90
  91 ```js
  92 /*eslint-env es6*/
  93
  94 var generator = function* () {
  95 }
  96 ```
  97
  98 When using the expression syntax `"middle"` will be enforced here:
  99
 100 ```js
 101 /*eslint-env es6*/
 102
 103 var generator = function * () {
 104 }
 105 ```
 106
 107 When using the expression syntax `"end"` will be enforced here:
 108
 109 ```js
 110 /*eslint-env es6*/
 111
 112 var generator = function *() {
 113 }
 114 ```
 115
 116 When using the expression syntax this is valid for both `"start"` and `"end"`:
 117
 118 ```js
 119 /*eslint-env es6*/
 120
 121 var generator = function*() {
 122 }
 123 ```
 124
 125 The shortened object literal syntax for generators is not affected by this rule.
 126
 127 ## When Not To Use It
 128
 129 If your project will not be using generators you do not need this rule.