How to make, when you scrolling down your page, the text button on the side nav become bold

Hello everyone, wondering to make the nav effect like in this video. When you scrolling, the text button on the side nav will become bold automatically.

https://www.youtube.com/watch?v=Ed5vW_SD-pU

From what I think, it’s that you would need to use tabs and when active set them bold
Another solution could be set them as link divs and select each section same logic, when active set them bold

thanks for your reply! I’ll give it try!