I need to support major modern browsers only (IE10+, FF, Chrome, Safari)
Can I make this substitution as I want to simplify my code base:
From:
Since the original asker said "I need to support major modern browsers only (IE10+, FF, Chrome, Safari)" it is obvious that onload, onerror, etc are the ways to go. Also, as of today, onreadystatechange is pretty much obsolete, as you are obviously not going to support anything that old that it supports onreadystatechange only.
To sum it up, forget about onreadystatechange.