How to add a class on scroll?

Question

JavaScript

There are many blocks on the site that have a standard class (hides an object) and an additional one (opens with animation. Animation on css).

Is there some easy way (plugin?) to add a class to a block that falls within the visible area of ​​the page?

There are many blocks and the classes of many blocks are the same.

Answer 1

https://codepen.io/dtkweb/pen/ExWqBgg