Processing.js is a wonderful tool. I'm not sure exactly what it is about Processing, but I find writing rich, graphical applications a breeze using Processing, and Processing.js Just Works in all major browsers!
To see cool stuff made with the original java version of Processing with source : http://openprocessing.org/
This website runs processing in a Java applet.
very cool. Do you have any demos that show explicitly how Processing.js can communicate with the document loaded in the browser, ... for instance, to enter a value on a form and then submit the form? This would open up new creative ways for user interaction.
Here's a couple of example that do exactly what you are talking about using Processing.js and the DOM with forms etc:
Very cool! I wonder why is processing a language as opposed to JS library?
I think you may be slightly confused. Processing is (historically) a visualization programming language (http://processing.org/ - implemented in Java). Processing.js is simply a port of that language to JavaScript, implemented as a JavaScript library.