Tryit Editor v2.9

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

<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>

<p id="demo"></p>

<script>
document.getElementById("myDIV").addEventListener("mousemove", myFunction);

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

function removeHandler() {
    document.getElementById("myDIV").removeEventListener("mousemove", myFunction);
}
</script>

</body>
</html>