javascript监听客户输入文字

<script>
<!--
function conWrite(obj,size,msg)
{
 if (document.getElementById(obj) != null)
 {
  var length = size - document.getElementById(obj).value.length;
  if (length > 0)
  {
   document.getElementById(msg).innerHTML="您当前还可以输入<strong><span class=/"font_green/">" + length + "</span></strong>个字符";
  }
  else
  {
   document.getElementById(msg).innerHTML="您当前输入的字符数已超过限制";
  }
 }
}
//-->
</script>请输入内容：
<textarea name="consult" id="consult" onMouseMove="conWrite('consult',30,'consultMsg')" onKeyUp="conWrite('consult',30,'consultMsg')" cols="50" rows="3" class="bird_form1" onFocus="if(this.value=='没有参考任何文献')this.value=''" onBlur="if(this.value=='')this.value='没有参考任何文献'">没有参考任何文献</textarea>

<table border=1>
  <tr>
    <td id="consultMsg"></td>
  </tr>
</table>