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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

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)

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 此页面的贡献者: yenshen, teoli, AlexChao, ziyunfei
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