Client-side Programming Overview
RadCheckBox provides a flexible client-side API. You can easily interact with the checkbox in the browser using the RadCheckBox client-side object. In addition to a variety of client-side events, the client-side object model lets you achieve complicated tasks while avoiding unnecessary post-backs.
Getting the RadCheckBox client-side object
RadCheckBox creates a client-side object with the ClientID of the button. You can obtain the reference using the following JavaScript code:
var checkBox = $find("<%= RadCheckBox1.ClientID %>");
or
var checkBox = $telerik.findCheckBox("<%= RadCheckBox1.ClientID %>");