All the sections will appear gradually

My JS add some class when the window load or scroll in any element which has .will-fadeIn. I use the operator % to add diferents class if the element is odd or even.

In CSS, I use keyframes to create the classes fadeInLeft and fadeInRight, these classes I use add on JS.

In my JS, if you pass false to the addFadeIn function, the elements will not keep reappearing