Will a JAWS script override a screen reader's ability to read the DOM?

I'm tasked with evaluating some legacy web pages (classic asp) for accessibility. You can assume the HTML is not perfectly formed and that it's loaded with inline javascript and that we make use of javascript libraries that vomit HTML to create dynamic features. It's a circus in there.

While I recognize that the obvious answer is to re-write the page(s), that's not an option in our given time tables. So I'm trying to find the best way to make the pages work with a screen reader. Here's what I think I know.

We can use JAWS scripting to instruct the browser how to read the page.
We can use ARIA attributes to give the pages better organization and structure.

Specifically, I'm trying to figure out: Question 1) If a JAWS script is present, will it be used exclusively by the browser/screen reader and ignore any improvements I make in the underling HTML structure?

Question 2) Could some well-place ARIA attributes give the page enough structure so that the default screen reader properties will work in an acceptable manner (without a JAWS script).

Question 3) I suspect the tough answer is that I would need to do both, which I'm trying to avoid because we barely have the capacity to do just one. But we don't want to lose a customer, of course. :-(

Many thanks for any input.

Solution

Instead of explaining only to JAWS how to access your pages, use JavaScript to explain it to any Assistive Technology (AT) for the web. I expect the same effort, while it will profit way more users.

In a JAWS script you would need to describe ways to access DOM nodes that are not accessible. That would include

speaking out information that you have to find elsewhere on the page
adding keyboard navigation where it's missing

Both can be done in JavaScript, probably even easier (you'll need to address DOM elements).

What you will need to avoid is restructuring the DOM and changes to classes, since those are most likely used by the scripts that generate them.

But I'd expect that adding attributes and keyboard handlers will do no harm to the existing scripts. Beware of already existing handlers for focus or keyboard events, though.

I would recommend making a list of attributes and handlers you suspect to conflict with the existing scripts, and searching the scripts for these, like onkeypress or onfocus event handlers.