How to Properly Modify JavaScript Files in a Parent Theme

I recently needed to modify a JavaScript file in a WordPress parent theme. The script was doing almost what I wanted, but not quite, so I wanted to make minor changes. In your case, you might want to entirely override a parent theme JavaScript file in your child theme, or even deactivate a parent theme JavaScript file altogether.

What Not to Do: Edit Parent Theme JavaScript Directly

The correct way to change a parent-theme JavaScript file is not to modify that file itself. The reason is simple: if your parent theme ever updates, you’ll lose all your changes. This is the whole point of WordPress child themes, and it’s as true for JavaScript as for anything else.

So all your changes will need to be in your child theme. If you’re making changes in your parent theme, you’re doing it wrong.

What to Do: Dequeue Parent Theme Script, then Enqueue Child Theme Script

You don’t edit or override parent theme JavaScript files. You stop the parent theme scripts from running, and replace them with similar scripts in the child theme.

Here’s the catch: WordPress doesn’t have a “template hierarchy” for JavaScript files, the way it does for PHP ones. In WordPress, there’s no such thing as “overriding JavaScript”—in a child theme, or anywhere else.