css3 - How to achieve the effect of each part of the page appearing as the scroll bar slides down?

Question

I watched a website, and as the scroll bar slid down, every part of the page showed the effects when it was first loaded.
These effects will only reappear if I refresh them again. How is this done? Is it written in the load of jquery?
Similar to the homepage of this website
http://www.itxdl.cn/brands/?b...

Answer 1

The one above is wrong
OK I looked at the source code.

Look at this library!
wow.jswow

This is the correct answer. When you have time, you can look at the source code of wow. It shouldn't be difficult.

Answer 2

The principle is very simple, hang a time to monitor the scrolling time, determine the current scrollTop and the offsettop of each element to operate