It's all about the selector. You can change your code to be something like this:
<div class="formbuilder">
<div class="active">Heading</div>
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
</div>
Then use this javascript:
$(document).ready(function () {
$('.formbuilder div').on('click', function () {
$('.formbuilder div').removeClass('active');
$(this).addClass('active');
});
});
The example in a working jsfiddle
See this api about the selector I used: http://api.jquery.com/descendant-selector/