<!DOCTYPE html>
<style>
div {
    position: absolute;
    width: 100px;
    height: 100px;
    font-size: 50px;
}

#expectation {
    background: red;
    transform: translate(1em, 1em);
}
</style>
<div id="expectation"></div>
<script>
var target = document.createElement('div');
target.style.background = 'green';
target.animate([
  {transform: "translate(1em, 1em)"},
  {transform: "translate(1em, 1em)"},
], {
  duration: 1000,
  iterations: Infinity,
});
document.body.appendChild(target);
</script>