Hi,
As you want to catch text change event on javascript side, you have two options.
1. Use onchange event. This event will fire javascript function as you loose focus from textbox.
2. Use keyup event, it will fire javascript function on each and every key up event.
Note:- As you don't want to fire server side event, do not use AutoPostBack="true" in textbox.
<asp:textbox id="txtMessage" runat="server" columns="40" rows="6" textmode="MultiLine" onchange="txtMsg_TextChanged(this)" ></asp:textbox>
<asp:textbox id="txtMessage1" runat="server" columns="40" rows="6" textmode="MultiLine" onkeyup="txtMsg_TextChanged1(this)" ></asp:textbox>
<script type="text/javascript">
function txtMsg_TextChanged(a) {
alert(a.value);
}
function txtMsg_TextChanged1(a) {
alert(a.value);
}
</script>
Try both, use as per your need.
Hope it helps you.
Thanks.