## 概述

`valueOf()` 方法返回一个被 `Number` 对象包装的原始值。

## 语法

    numObj.valueOf()

### 返回值

表示指定 `Number` 对象的原始值的数字

## 描述

该方法通常是由 JavaScript 引擎在内部隐式调用的，而不是由用户在代码中显式调用的。

## 示例

    var numObj = new Number(10);
    console.log(typeof numObj); // object

    var num = numObj.valueOf();
    console.log(num);           // 10
    console.log(typeof num);    // number

## 规范

规范名称 | 规范状态 | 备注
--- | --- | ---
ECMAScript 1st Edition. | Standard |
ECMAScript 5.1 (ECMA-262) Number.prototype.valueOf | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) Number.prototype.valueOf | Standard |

## 浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

- Desktop
- Mobile

Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari
--- | --- | --- | --- | --- | ---
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes)

Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile
--- | --- | --- | --- | --- | --- | ---
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes)

## 相关链接

- `Number.prototype.toSource()`