Asp.net实时显示文本框字数实现代码

<script language="javascript" type="text/javascript">
function countNum()
{
var count=document.getElementById("txtText").value.length;
document.getElementById("lblCount").value=count;
}
</script>

<asp:TextBox ID="txtText" name="txtText" runat="server" Columns="80" Rows="8" TextMode="MultiLine"
Width="650px" Height="150px" onkeydown="countNum();"
onmousemove="countNum();" onmouseout="countNum();" onkeyup="countNum();"></asp:TextBox>
（已输入<input id="lblCount" type="button" style="border-style: none; background: none;" value="0" />字）