Without any JavaScript library, if you want to check whether an element exists, in our case, an element with the id myDiv, here is what you do:
<script>
if (document.getElementById('myDiv')) {
alert('myDiv exists');
}
</script>
In jQuery, here is what you can do:
<script>
if ($('#myDiv').length) {
alert('myDiv exists');
}
</script>
