The canvas API is accessed via a canvas context object. You get the context by calling the getContext() method of the <canvas> element, passing in a string parameter that defines the type of the context you want:

var context = $("canvas")[0].getContext("2d");

The only valid context type parameter you can pass into getContext() at this time is "2d". This begs the question, "Is there a 3D context?" The answer is no, there is not. But we can always hope for one in the future.