Page Specific Javascript

Hi!

I am a beginner in JS and wanted to try doing a multi page website that would use GSAP and JS for simple interactivity. I would like to have an advice over what is a better practice, to have many small page specific JS files or to combine all in one big JS file? If to combine all in one main.js what would be the best option - to have a function only run if body.classList.contains(".page1") - for page specific JS or some other way?