eslint/docs/rules/generator-star.md

   1 # generator-star: enforce consistent spacing around the asterisk in generator functions
   2
   3 (removed) This rule was **removed** in ESLint v1.0 and **replaced** by the [generator-star-spacing](generator-star-spacing.md) rule.
   4
   5 Generators are a new type of function in ECMAScript 6 that can return multiple values over time.
   6 These special functions are indicated by placing an `*` after the `function` keyword.
   7
   8 Here is an example of a generator function:
   9
  10 ```js
  11 /*eslint-env es6*/
  12
  13 function* generator() {
  14     yield "44";
  15     yield "55";
  16 }
  17 ```
  18
  19 This is also valid:
  20
  21 ```js
  22 /*eslint-env es6*/
  23
  24 function *generator() {
  25     yield "44";
  26     yield "55";
  27 }
  28 ```
  29
  30 This is valid as well:
  31
  32 ```js
  33 /*eslint-env es6*/
  34
  35 function * generator() {
  36     yield "44";
  37     yield "55";
  38 }
  39 ```
  40
  41 To keep a sense of consistency when using generators this rule enforces a single position for the `*`.
  42
  43 ## Rule Details
  44
  45 This rule enforces that the `*` is either placed next to the `function` keyword or the name of the function. The single
  46 option for this rule is a string specifying the placement of the asterisk. For this option you may pass
  47 `"start"`, `"middle"` or `"end"`. The default is `"end"`.
  48
  49 You can set the style in configuration like this:
  50
  51 ```json
  52 "generator-star": ["error", "start"]
  53 ```
  54
  55 When using `"start"` this placement will be enforced:
  56
  57 ```js
  58 /*eslint-env es6*/
  59
  60 function* generator() {
  61 }
  62 ```
  63
  64 When using `"middle"` this placement will be enforced:
  65
  66 ```js
  67 /*eslint-env es6*/
  68
  69 function * generator() {
  70 }
  71 ```
  72
  73 When using `"end"` this placement will be enforced:
  74
  75 ```js
  76 /*eslint-env es6*/
  77
  78 function *generator() {
  79 }
  80 ```
  81
  82 When using the expression syntax `"start"` will be enforced here:
  83
  84 ```js
  85 /*eslint-env es6*/
  86
  87 var generator = function* () {
  88 }
  89 ```
  90
  91 When using the expression syntax `"middle"` will be enforced here:
  92
  93 ```js
  94 /*eslint-env es6*/
  95
  96 var generator = function * () {
  97 }
  98 ```
  99
 100 When using the expression syntax `"end"` will be enforced here:
 101
 102 ```js
 103 /*eslint-env es6*/
 104
 105 var generator = function *() {
 106 }
 107 ```
 108
 109 When using the expression syntax this is valid for both `"start"` and `"end"`:
 110
 111 ```js
 112 /*eslint-env es6*/
 113
 114 var generator = function*() {
 115 }
 116 ```
 117
 118 The shortened object literal syntax for generators is not affected by this rule.
 119
 120 ## When Not To Use It
 121
 122 If your project will not be using generators you do not need this rule.
 123
 124 ## Further Reading
 125
 126 * [Understanding ES6: Generators](https://leanpub.com/understandinges6/read/#leanpub-auto-generators)