How to make a class change when scale pages?

Question

Hi to all, for example this design
Menu fixed, how to make so that when you scroll a website, say 300px, the menu added a class scroll
Well, the class will be assigned to the other text color in the menu.

The reverse scroll, the class was removed.

Answer 1

This question appears here more often than rabbits breed. Try and use the search.

P. s:Here, I wrote, for example: How to make a block when you scroll?