String.length

概述

length 属性表示一个字符串的长度。

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

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 is has a length of " + empty.length);
/* "The empty string is 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)
String.prototype.length
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
String.prototype.length
Standard  

浏览器兼容性

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