<script>
var rng = document.querySelector("input");

read("mousedown");
read("mousemove");

function read(evtType) {
  rng.addEventListener(evtType, function() {
    window.requestAnimationFrame(function () {
      document.querySelector("div").innerHTML = rng.value;
    });
  });
}
</script>
<div>50</div><input type="range"/>