After some thought, I realized that it's possible to detect when a CSS animation starts, finishes, or repeats by using the animationstart, animationiteration, and animationend events. For example:
document.getElementById('identifier')
.addEventListener("animationstart", function(){
// do something...
});
But then I started wondering, is there a way to determine where we are within a CSS animation? Like, how can I listen for when we reach the 50% mark of a keyframe animation, as shown below:
<!DOCTYPE html>
<html>
<head>
<style>
#animateDiv {
width: 100px;
height: 100px;
background-color: red;
position: relative;
animation-name: example;
animation-duration: 4s;
}
@keyframes example {
0% {background-color:red; left:0px; top:0px;}
25% {background-color:yellow; left:200px; top:0px;}
50% {background-color:blue; left:200px; top:200px;}
75% {background-color:green; left:0px; top:200px;}
100% {background-color:red; left:0px; top:0px;}
}
</style>
</head>
<body>
<div id="animateDiv"></div>
<script>
// What should I do here to listen for the event at 50% of the keyframes?
document.getElementById('animateDiv').addEventListener('animation at 50%?', function() {
console.log('got it');
})
</script>
</body>
</html>