Size属性将会返回`Set`对象中元素的个数。

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## 描述

`size`的值是一个整数，表示`Set`对象有多少条目。`size`的集合访问函数是`undefined`; 你不能改变这个属性。

## 例子

### 使用`size`

    var mySet = new Set();
    mySet.add(1);
    mySet.add(5);
    mySet.add("some text")

    mySet.size; // 3

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 2015 (6th Edition, ECMA-262) Set.prototype.size | Standard | 初始定义
ECMAScript Latest Draft (ECMA-262) Set.prototype.size | Draft |

## 浏览器兼容

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

| Desktop | Mobile | Server
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet | Node.js
`size` | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 19 Notes Full support 19 Notes Notes From Firefox 13 to Firefox 18, the `size` property was implemented as a `Set.prototype.size()` method, this has been changed to a property in later versions conform to the ECMAScript 2015 specification. | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 19 Notes Full support 19 Notes Notes From Firefox 13 to Firefox 18, the `size` property was implemented as a `Set.prototype.size()` method, this has been changed to a property in later versions conform to the ECMAScript 2015 specification. | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12

### Legend

Full support
  Full support
See implementation notes.
  See implementation notes.

## 参见

- `Set`