JS动态就是文本框字符数目

<scrīpt type="text/javascrīpt">
<!--
  var maxLen=100;
   function checkMaxInput(obj)
     {
       var m=obj.value.length;
       var n=m;
       var j=0;
       var remLen1 = document.getElementById("remLen1");
       var remLen2 = document.getElementById("remLen2");
       var remLen3 = document.getElementById("remLen3");
       var remLen4 = document.getElementById("remLen4");
       var remLen5 = document.getElementById("remLen5");

        for (var i=0;i<m;i++)
         {
          if (obj.value.charCodeAt(i)<0||obj.value.charCodeAt(i)>161)
    {
            n=n+1;
            if ( i < 100 )
     {
               j=j+1;
            }
    }
         }
 
        if(n>maxLen)
         {
            obj.value=obj.value.substring(0,maxLen-j);
 
            remLen1.innerHTML='[最大可输入';
            remLen2.innerHTML=maxLen;
         remLen3.innerHTML='字符，';
         remLen4.innerHTML='您已达到输入上限！';
         remLen5.innerHTML=']';
          }
        else
          {
      remLen1.innerHTML='[最大可输入';
            remLen2.innerHTML=maxLen;
         remLen3.innerHTML='字符，还可输入';
         remLen4.innerHTML=maxLen-n;
         remLen5.innerHTML='字符]';
     }
     } 
//-->
</scrīpt>
 
 
<textarea name="creditcontent" cols="45" rows="5" ōnKeyDown="checkMaxInput(this)" ōnKeyUp="checkMaxInput(this)" ōnBlur="checkMaxInput(this)" class="12pxbd"></textarea>
<br>
<font id="remLen1"></font>
<font color=red id="remLen2"></font>
<font id="remLen3"></font>
<font color=red id="remLen4"></font>
<font id="remLen5"></font>