So here's a simple processing demo I did a while ago, ported to p5.js, a library allowing you to essentially write processing in JavaScript, using an HTML canvas! As you will see when running the demo, JavaScript performance is not really where you'd like it to be when doing animation :) The JavaScript engine of your browser makes a huge difference here. I recommend running this in Chrome, it's quite noticably faster than Firefox.

Click here to run the demo

Source code