Regarding Java Script Function

First thing first - You may use multiple ways to refister javascript functions on client side, please note that javascript is a client side scripting and all its functions will be executed on the web client i.e. browser.

 

When you register any function on client side e.g. onchange then first control is rendered on the page and then onchange event is attached to the DOM, however in other scenario - your control is rendered on a page with event already attached to it.