How to add a JavaScript callback for the 'Agile Uploader' version 3?
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On the web page for the Agile Uploader plug-in, where he writes about the release of version 3, its developer writes:

*"The JavaScript callbacks are no more. Instead, there's more of an "event" system. This leaves you to define one event handler function should you like to build your own JavaScript to work with Agile Uploader."*

Needless to say, having a callback function is very important. However, I don't really understand what he means by "defining one event handler function...".
In short, I need a callback function but I don't understand how to add one with version 3 of this plug-in. How do I do it?

Please help