Introduction to HTML5 Canvas - HTML5 Canvas - page 24

Retrieving the 2D Context

Finally, we need to get a reference to the 2D context so that we can manipulate it. HTML5
Canvas is designed to work with multiple contexts, including a proposed 3D context.
However, for the purposes of this topic, we need to get only the 2D context:

var var context = theCanvas . getContext ( "2d" );