AnimusJS is the solution for combine JS and CSS animations.

With AnimusJS, you can create animations Changing CSS Classes or using JavaScript Functions very easy!

Live Example: http://codepen.io/soutomario/pen/akrwxp?editors=0010

First things first...

npm install animusjs

or

git clone https://github.com/soutomario/animusjs.git

After it you need to include the library

<script src="js/animusjs.min.js"></script>
<script src="https://mariosouto.com/animusjs/js/animusjs.min.js"></script> <!-- Or just import from my website -->

and then you init the magic!

animusjs.init();

Now to see if everything is working, lets create a simple HTML

<img anim-in="active-my-animation" anim-out="active-my-animation" src="placehold.it/1920x1080">
<img anim-in="active-my-animation" anim-out="active-my-animation" src="placehold.it/1920x1080">
<img anim-in="active-my-animation" anim-out="active" src="placehold.it/1920x1080">
<img anim-in="active-my-animation" anim-out="active-my-animation" src="placehold.it/1920x1080">

If you look, we add the anim-in and anim-out parameters, they are used by AnimusJS to trigger your animation.

Well, at this points you just need to create a CSS to make something with the images:

img {
  opacity: 0;
  transform: translateX(-50px);
  transition: .5s ease-in-out;
}
img.active-my-animation {
  opacity: 1;
  transform: translateX(0px);
}

Now when you scroll the page you will see everything animated!

• anim-type Define what kind of action you want to trigger. By default the AnimusJs uses anim-type="class", but you can pass anim-type="function" too (In this case a JavaScript function will be called).

• anim-in Do some action when the users scroll down.

• anim-out Do some action when the users scroll up.

• anim-in-out Do some action when you scroll down and call the same action when you scroll up.

If you use a javascript function you have to pass 2 parameters like this example

function active(element, options) {
	if(options.status === 'animate') {
		element.classList.add('active');
	}
	if(options.status === 'reverse') {
		element.classList.remove('active');
	}
}