Question: I'm working on a codebase with multiple blocks of code setting some behavior on document.ready() (jQuery). Is there a way to enforce that one specific block is called before any of the others? 

Background:
I need to detect JS errors in an automated testing environment, so I need the code that starts logging JS errors to execute before any other JS code executes.

Answer: 
`document.ready()` callbacks are called in the order they were registered. If you register your testing callback first, it will be called first.

Also if your testing code does not actually need to manipulate the DOM, then you may be able to run it as the code is parsed and not wait until the DOM is ready which would run before the other `document.ready()` callbacks get called. Or, perhaps you could run part of your testing code immediately and defer only the part that uses the DOM until `document.ready()`.

Another idea is (for testing purposes only) you could run with a slightly modified version of jQuery that added a flag to `document.ready()` that when passed and set to `true` indicated to call that function first or you could add a new method `document.readyFirst()` that would call your function first. This would involve minor changes to the `document.ready()` processing code in jQuery.
You can execute the logging start code in DOMReady and other initialization in load. Or you could make your own initialization manager which calls your logging start code first and then all other initialization callbacks (provided that those are registered with your manager and not jQuery, unless you want to hack jQuery and extract them from there, which I don't advise).