string.length
string.length
属性表示一个字符串的长度。
语法
str.length
描述
该属性返回字符串中字符编码单元的数量。JavaScript 使用 UTF-16 编码，该编码使用一个 16 比特的编码单元来表示大部分常见的字符，使用两个代码单元表示不常用的字符。因此 length 返回值可能与字符串中实际的字符数量不相同。
空字符串的 length 为 0。
静态属性 String.length 返回 1。
示例
基本示例
var x = 'Mozilla';
var empty = '';
console.log('Mozilla is ' + x.length + ' code units long'
/* "Mozilla is 7 code units long" */
console.log('The empty string has a length of ' + empty.length
/* "The empty string has a length of 0" */
规范
| Specification | Status | Comment |
|---|---|---|
| ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.0. |
| ECMAScript 5.1 (ECMA-262)The definition of 'String.prototype.length' in that specification. | Standard | |
| ECMAScript 2015 (6th Edition, ECMA-262)The definition of 'String.prototype.length' in that specification. | Standard | |
| ECMAScript Latest Draft (ECMA-262)The definition of 'String.prototype.length' in that specification. | Living Standard | |
浏览器兼容性
| Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
