Include Jquery Library in head section
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js" type="text/javascript"></script>
<script src="modules/mod_djmenu/assets/js/catimage.js" type="text/javascript"></script>
<script>
$(document).ready(function(){
$("#navbar").hide();
});
</script>