breaking JS for scroll-to-top

Hey there,

I think the best idea would be to make your CSS more specific. The scroll-to-top arrow is in the footer, so you could target all links inside the main content area like this without affecting it:

.main a { 
  scroll-behavior: smooth; 
}

That will affect all links besides ones in the header and footer.

Okey, but where should I look to remove its JS codes?

You’ll need to dequeue the Javascript file, like this:

function my_dequeue_script() {
  wp_dequeue_script( 'ct-mission-news-js');
}
add_action( 'wp_enqueue_scripts', 'my_dequeue_script' );

Then you can copy all of the JS from the production.js file in Mission News into a JS file in your own child theme and enqueue that JS file. You can remove the bit of code at the bottom that handles the scroll-to-top arrow.

Before that, I tried to delete the code from js/build/production.js and js/build/production.min.js files in the main theme, or rather delete the postponement part, but it did not work.

Deleting that code from production.min.js would work as long as you clear the cache afterwards so the new version of the file gets loaded. However, this change would be overridden every time Mission News updates, so you’d have to do this repeatedly. That’s why it’s better to make a change in the child theme instead.