*
value: 值；
byteLength：数据库字节长度
title：字段中文名称
attribute：属性名称
使用方法说明：
添加 （1） οnkeyup="limitLength(this.value,100,'名称','name')"
            (2)    id="name" 或【struts标签】styleId="name"
注意：id名称和 attribute属性名称要一样
      
例子：<textarea    name="explain" id="explain" οnkeyup="limitLength(value,5,'语义说明','explain')" >  
或
<input type="text"     name="explain"    id="explain" οnkeyup="limitLength(value,5,'语义说明','explain')" >
*/

function limitLength(value, byteLength, title, attribute) {
         var newvalue = value.replace(/[^/x00-/xff]/g, "**");
         var length = newvalue.length;
  
         //当填写的字节数小于设置的字节数
        if (length * 1 <=byteLength * 1){
              return;
        }
        var limitDate = newvalue.substr(0, byteLength);
        var count = 0;
        var limitvalue = "";
       for (var i = 0; i < limitDate.length; i++) {
               var flat = limitDate.substr(i, 1);
              if (flat == "*") {
                    count++;
              }
       }
       var size = 0;
       var istar = newvalue.substr(byteLength * 1 - 1, 1);//校验点是否为“×”
   
      //if 基点是×; 判断在基点内有×为偶数还是奇数  
       if (count % 2 == 0) {
                //当为偶数时
              size = count / 2 + (byteLength * 1 - count);
              limitvalue = value.substr(0, size);
      } else {
              //当为奇数时
              size = (count - 1) / 2 + (byteLength * 1 - count);
              limitvalue = value.substr(0, size);
      }
     alert(title + "最大输入" + byteLength + "个字节（相当于"+byteLength /2+"个汉字）！");
     document.getElementById(attribute).value = limitvalue;
     return;
}