Site lag and running slow loading pages

I am loading a site with quite a bit of JavaScript and as the page is loading on my wait I notice quote a bit of lag & that "not responding" message will show for a bit and then go away.

• Any help on optimization and what the issue is and what I should do. I try to include clean code but their is a lot of js running and onclick animating.
• I dont want to shortcut and run in all through CND. Would it even help much or would it eventually run back to the same issue later