49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
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---
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title: String Length
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localeTitle: 字符串长度
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---
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`length`属性表示字符串的长度。
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## 句法
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```
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str.length
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```
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[MDN链接](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length) | [MSDN链接](https://msdn.microsoft.com/en-us/LIBRary/3d616214%28v=vs.94%29.aspx)
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## 描述
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此属性返回字符串中的代码单元数。 UTF-16是JavaScript使用的字符串格式，使用单个16位代码单元来表示最常见的字符，但需要使用两个代码单元来表示不常用的字符，因此有可能将长度返回的值返回到不匹配字符串中的实际字符数。
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对于空字符串，长度为0。
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静态属性`String.length`返回值1。
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## 例子
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```
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var x = 'Mozilla';
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var empty = '';
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console.log('Mozilla is ' + x.length + ' code units long');
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/* "Mozilla is 7 code units long" */
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console.log('The empty string has a length of ' + empty.length);
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/* "The empty string has a length of 0" */
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var str = "every good boy does fine";
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var start = 0;
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var end = str.length - 1;
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var tmp = "";
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var arr = new Array(end);
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while (end >= 0) {
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arr[start++] = str.charAt(end--);
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}
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// Join the elements of the array with a
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var str2 = arr.join('');
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document.write(str2);
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// Output: enif seod yob doog yreve
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```
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