Custom AJAX Script for Filters? No reload page?

I’m looking at this demo – https://demo.themeum.com/wordpress/skillate/courses/

It looks like the custom filters are using AJAX which don’t reload the page.

However, on my website the page reloads whenever selecting a filter. The same applies to other demos of your plugin.

Is there a function or custom script that we can install to enable this feature?

thank you