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<!DOCTYPE html>
<html>
<head>
<style> 
div {
  width: 100px;
  height: 100px;
  background: red;
  position: relative;
  animation: mymove 2s infinite;
}
@keyframes mymove {
  from {left: 0px;}
  to {left: 200px;}
}
@keyframes myNEWmove {
  from {width: 0px;}
  to {width: 500px; background: blue;}
}
</style>
</head>
<body>
<h1>Change animation-name with JavaScript</h1>
<p>Click the "Try it" button to change what @keyframes to use in the animation:</p>
<button onclick="myFunction()">Try it</button>
<div id="myDIV"></div>
<script>
function myFunction() {
  document.getElementById("myDIV").style.animationName = "myNEWmove";
}
</script>
</body>
</html>