以指定编码对字符串进行截取

假设有字符串“朱元璋”，截取限定的长度为7字节

截取编码为utf-8    结果为“朱”

截取编码为gb2312时  结果为“朱”

 

字符串为“hello朱元璋”，截取限定的长度为13字节

截取编码为utf-8    结果为“hello朱元”

 

这里的问题就是gbk编码占位2个字节，而utf-8占位3个字节，完整的示例代码：

   1:  
   2: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
   3: <html>
   4:  <head>
   5:   <title> new document </title>
   6:   <meta name="generator" content="editplus" />
   7:   <meta name="author" content="" />
   8:   <meta name="keywords" content="" />
   9:   <meta name="description" content="" />
  10:   <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  11:  </head>
  12:  
  13:  <body>
  14:   <script type="text/javascript">
  15: function getRealLen(str, isUTF8) {
  16:     if (typeof str != 'string') {
  17:         return 0;
  18:     }
  19:     
  20:     if (!isUTF8) {
  21:         return str.replace(/[^\x00-\xFF]/g, 'xx').length;
  22:     } else {
  23:         var tempStr = str.replace(/[\x00-\xFF]/g, '');
  24:         return (str.length - tempStr.length) + Math.floor(encodeURI(tempStr).length / 3);
  25:     }
  26: }
  27:  
  28: function uniLeft(str, isUTF8, len, suffix) {
  29:     var str = str.toString();
  30:     var len = len * 1;
  31:     var suffix = suffix || "";
  32:  
  33:     if (isNaN(len)) {
  34:         return str;
  35:     }
  36:  
  37:     var uniLen = getRealLen(str, isUTF8),tempStr = '';
  38:     
  39:     if (uniLen <= len) {
  40:         return str.substr(0);
  41:     }
  42:     
  43:     for (var i = Math.floor(len / 2); i< uniLen; i++) {
  44:         tempStr = str.substr(0, i);
  45:  
  46:         if (getRealLen(tempStr, isUTF8) >= len || getRealLen(str.substr(0, i+1), isUTF8) > len) {
  47:             return tempStr;
  48:         }
  49:     }
  50: }
  51:  
  52: var str_1 = '朱元璋';
  53: var str_2 = 'hello朱元璋';
  54:  
  55: document.write( uniLeft(str_1, false, 3) + "<br/>");//gb2312
  56: document.write( uniLeft(str_2, true, 13) );//utf-8
  57: </script>
  58:  </body>
  59: </html>

 

这里从len/2开始试着截取字符串，截取后调用getRealLen方法获取真实长度，判断是否超出限定的长度

posted @ 2011-03-21 23:34  meteoric_cry  阅读(609)  评论(0)    收藏  举报