`toUpperCase()` 将调用该方法的字符串值转换为大写形式，并返回。

## 语法

    str.toUpperCase()

## 描述

`toUpperCase` 将调用该方法的字符串值转换为大写形式，并返回。`toUpperCase` 方法不影响字符串本身的值。

## 示例

### 例子：使用 `toUpperCase`

    ​console.log( "alphabet".toUpperCase() ); // "ALPHABET"

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262) String.prototype.toUpperCase | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) String.prototype.toUpperCase | 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

- `String.prototype.toLocaleLowerCase()`
- `String.prototype.toLocaleUpperCase()`
- `String.prototype.toLowerCase()`