import 8.41.0 source

[pve-eslint.git] / eslint / docs / src / rules / no-iterator.md

---
title: no-iterator
rule_type: suggestion
further_reading:
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators
- https://kangax.github.io/es5-compat-table/es6/#Iterators
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features#Object_methods
---


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:

```js
Foo.prototype.__iterator__ = function() {
    return new FooIterator(this);
}
```

You should use ECMAScript 6 iterators and generators instead.

## Rule Details

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.

Examples of **incorrect** code for this rule:

::: incorrect

```js
/*eslint no-iterator: "error"*/

Foo.prototype.__iterator__ = function() {
    return new FooIterator(this);
};

foo.__iterator__ = function () {};

foo["__iterator__"] = function () {};

```

:::

Examples of **correct** code for this rule:

::: correct

```js
/*eslint no-iterator: "error"*/

var __iterator__ = foo; // Not using the `__iterator__` property.
```

:::