W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style>
#myDIV {
  background-color: coral;
  border: 1px solid;
  padding: 50px;
  color: white;
}
</style>
</head>
<body>

<p>This example demonstrates a solution that will work for all browsers.</p>

<div id="myDIV">This div element has an onmousemove event handler that displays a random number every time you move your mouse inside this orange field.
  <p>Click the button to remove the DIV's event handler.</p>
  <button onclick="removeHandler()" id="myBtn">Try it</button>
</div>

function myFunction() {
  document.getElementById("demo").innerHTML = Math.random();
}

function removeHandler() {
  if (x.removeEventListener) {
    x.removeEventListener("mousemove", myFunction);
  } else if (x.detachEvent) {
    x.detachEvent("onmousemove", myFunction);
  }
}
</script>

</body>
</html>