## 概述

`Math.sqrt()` 函数返回一个数的平方根，即：

∀x≥0,M a t h.s q r t(x)=x=the unique y≥0 such that y 2=x\forall x \geq 0, \mathtt{Math.sqrt(x)} = \sqrt{x} = \text{the unique} \; y \geq 0 \; \text{such that} \; y^2 = x

## 语法

    Math.sqrt(x)

### 参数

`x`
  一个数值

## 描述

如果参数 `number` 为负值，则 `sqrt` 返回 `NaN`。

由于 `sqrt` 是 `Math` 的静态方法，所以应该像这样使用：`Math.sqrt()`，而不是作为你创建的 `Math` 实例的方法。

## 示例

### 例子：使用 `Math.sqrt`

    Math.sqrt(9); // 3
    Math.sqrt(2); // 1.414213562373095

    Math.sqrt(1);  // 1
    Math.sqrt(0);  // 0
    Math.sqrt(-1); // NaN

## 规范

规范版本 | 规范状态 | 注解
--- | --- | ---
ECMAScript 1st Edition. Implemented in JavaScript 1.0 | Standard | Initial definition.
ECMAScript 5.1 (ECMA-262) Math.sqrt | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) Math.sqrt | 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)