OnFocus
The OnFocus client-side event handler is called when the input control gets focus.
The OnFocus event is supported by all RadInput controls, if they are not ReadOnly .
Two parameters are passed to the event handler:
sender is the input control.
eventArgs is an instance of Sys.EventArgs.
The following example uses the OnFocus event to show an alert:
<telerik:RadTextBox RenderMode="Lightweight" ID="RadTextBox1" runat="server">
<ClientEvents OnFocus="Focus" />
</telerik:RadTextBox>
<script type="text/javascript">
function Focus(sender, eventArgs)
{
alert(sender.get_id());
}
</script>