eslint/docs/src/rules/no-iterator.md

   1 ---
   2 title: no-iterator
   3 layout: doc
   4 rule_type: suggestion
   5 further_reading:
   6 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators
   7 - https://kangax.github.io/es5-compat-table/es6/#Iterators
   8 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features#Object_methods
   9 ---
  10
  11
  12 The `__iterator__` property was a SpiderMonkey extension to JavaScript that could be used to create custom iterators that are compatible with JavaScript's `for in` and `for each` constructs. However, this property is now obsolete, so it should not be used. Here's an example of how this used to work:
  13
  14 ```js
  15 Foo.prototype.__iterator__ = function() {
  16     return new FooIterator(this);
  17 }
  18 ```
  19
  20 You should use ECMAScript 6 iterators and generators instead.
  21
  22 ## Rule Details
  23
  24 This rule is aimed at preventing errors that may arise from using the `__iterator__` property, which is not implemented in several browsers. As such, it will warn whenever it encounters the `__iterator__` property.
  25
  26 Examples of **incorrect** code for this rule:
  27
  28 ::: incorrect
  29
  30 ```js
  31 /*eslint no-iterator: "error"*/
  32
  33 Foo.prototype.__iterator__ = function() {
  34     return new FooIterator(this);
  35 };
  36
  37 foo.__iterator__ = function () {};
  38
  39 foo["__iterator__"] = function () {};
  40
  41 ```
  42
  43 :::
  44
  45 Examples of **correct** code for this rule:
  46
  47 ::: correct
  48
  49 ```js
  50 /*eslint no-iterator: "error"*/
  51
  52 var __iterator__ = foo; // Not using the `__iterator__` property.
  53 ```
  54
  55 :::