Allow Numeric only in a textbox using javascript

Allow Numeric only in a textbox using javascript:

<script language="javascript" type="text/javascript">

function allowNumericOnly(evt) {

var charCode = (evt.which) ? evt.which : event.keyCode;

if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57))

return false;

return true;

}

</script>

<asp:TextBox ID="txtSalary" runat="server" onkeypress="return allowNumericOnly(event)"></asp:TextBox>