is using "on_click" function OK?

I need to detect if user clicked image in my list (template for each list entry is image and some text). in the sample app “ipad menu” there is text just about what i need:

The DHTMLX Touch library provides a ready solution to set onclick event listener – on_click object. You need to add className of a necessary HTML container into this object and set event handler as a property value:

$$(“submenu”).on_click[“buy_outside”] = function(e){

but there is no word about this function in the official docs.
So is it OK to use it and there is just missing docs, or is this some internal function that could be removed/work unstable/something else and it shouldn’t be used?

This functionality is fully legal and will present in next versions as well. ( it will be added to the documentation )