javascript監聽客戶輸入文字

<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="您當前還可以輸入<strong><span class=/"font_green/">" + length + "</span></strong>個字元";
  }
  else
  {
   document.getElementById(msg).innerHTML="您當前輸入的字元數已超過限制";
  }
 }
}
//-->
</script>請輸入內容：
<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=='沒有參考任何文獻')this.value=''" onBlur="if(this.value=='')this.value='沒有參考任何文獻'">沒有參考任何文獻</textarea>

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