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)
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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
orundefined
, 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
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Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
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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) |