JumboTron takes multiple independent canvases on the same page, and presents them to your JavaScript program as a single canvas. Consider it a jumbotron for your webpage.
// Take all of your pages' canvases, and make them into a super canvas.
var canvas = new JumboTron(document.getElementsByTagName('canvas'));
// Use 'canvas' like a regular canvas.
// Grab its context, draw stuff, etc.
var ctx = canvas.getContext('2d');
Basically, you should be able to drop JumboTron into an unmodified application; just tell the application to use the JumboTron as the canvas.
JumboTron constructs an invisible canvas that is the size of your combined canvases. It applies all changes to this canvas, and then updates the canvases on your web page.