<script src="https://code.jquery.com/jquery-3.1.0.js"></script>
<div class="a">i'm first loaded content. You cant see me with your eyes or inspect element, but you can see me in view-source</div>
<script>
$(function(){
    $('#a').html('i am content that created on the air. you cant found me in view-source');
});
</script>