If the latest flashy HTML5 experiments have you fired up to experiment with HTML5′s canvas element yourself, one seasoned developer has some advice for newcomers — particularly those coming from Flash backgrounds.
Perhaps the most useful tidbit in the article is that “bitmap operations are very processing expensive,” and whenever possible you should reduce and reuse as many pixels as you can between frames. While browsers are getting faster, optimization will always be key (the same is true of Flash animations).
Another thing Hakim recommends you keep in mind if you’re coming from a Flash background is that, “unlike the Flash Player’s redraw regions, this management of ‘dirty rectangles’ needs to be done manually for canvas.” Think of it as garbage collection — like C or C++, you’re in charge of cleaning up after your code when it comes to redrawing in Canvas.
Along the same lines is his tip for clearing your canvas: just reset the width and height. This is also good know if you want to avoid clearing your canvas.