jQuery upgrade issues: jQuery.fn is not working properly after upgraded from 1.6.4 to 1.12.4 getting $(...). ****** is not a function

[ilapavuluri]

Description

I am currently using jQuery 1.6.4, in the process of upgrade I moved to 1.12.4, I am adding some additional functions to jQuery like this:

jQuery.fn.xyz= function(g, b) {
......
}

I tried jQuery.fn.extend as well, both are loading the given function, but again it is clearing them and at the time of usage I am getting:

$(...). ****** is not a function, because at this time my function is not part of jQuery functions list.

usage:
$("#editor1234").xyz('val')

If I am back to old jQuery(1.6.4), it is working perfectly fine.

Link to test case

_{EDIT by @mgol: I converted this to a discussion as it's not really a proper bug report but likely a local setup issue.}