String.prototype.toUpperCase()

toUpperCase()  方法返回一个将调用字符串转换为大写形式的值。(如果这个值不是字符串则会被变成字符串)

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

语法

str.toUpperCase()

返回值

一个表示调用字串转换成大写格式的新字符串。

异议

TypeError
When called on null or undefined, for example,  String.prototype.toUpperCase.call(undefined).

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因为JavaScript的strings是immutable的(不可改变的)。

示例

例子:使用 toUpperCase

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

将非字符串形式的 this 值转换成字符串

这个方法会将任何非字符串形式的值转换成字符串, 当你把这个值的 this 设置成一个不是字符串的值时:

const a = String.prototype.toUpperCase.call({
  toString: function toString() {
    return 'abcdef';
  }
});

const b = String.prototype.toUpperCase.call(true);

// prints out 'ABCDEF TRUE'.
console.log(a, b);

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!
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