js 字符串长度截取

 <script>
   function cutstr(str, len) {
     var temp,
         icount = 0,
         patrn = /[^\x00-\xff]/,
         strre = "";
     for (var i = 0; i < str.length; i++) {
         if (icount < len - 1) {
             temp = str.substr(i, 1);
                 if (patrn.exec(temp) == null) {
                    icount = icount + 1
             } else {
                 icount = icount + 2
             }
             strre += temp
             } else {
             break;
         }
     }
     return strre + "..."
   }
   console.log(cutstr('helloWorld', 3))
 </script>