How to set focus after the text in the textbox

This code demonstrate how to set focus after the text in the textbox.

Design code :

<input type="button" id="idbtn" value="Set" onclick="func();" />

 <asp:TextBox ID="TextBox1" runat="server" Text="hi"></asp:TextBox>

JavaScript code :

<script language="javascript">

function func()

{

    var txt1= document.getElementById("TextBox1");

    txt1.focus();//set focus

    txt1.value = txt1.value; //set value

}

</script>

Thanks,
Abhay