NextJS: Vanilla JavaScript, Possible or not?

Newbie to ReactJS and NextJS here, was wondering if it is possible to add JavaScript to HTML classNames in NextJS. For example trying to create a parallax effect requires a certain package to be installed through npm to be able to get parallax working.

Example question: How do I add a javascript effect to this image code?

<Image className={styles.bg}
    src="/../public/bg.jpg"
    // width={2049}
    // height={2049}
    // objectFit="cover"
    layout="fill"
    quality={100}
  />

So my question is how do I add the below code to make my javascript effect work:

let bg = document.getElementById("bg");

    window.addEventListener('scroll', function() {
      var value = window.scrollY;

      bg.style.top = value * 0.5 + 'px';
      moon.style.left = -value * 0.5 + 'px';