I must say, this is pretty impressive. I am not too experience so maybe not, but the use of canvas and the short amount of code to make such a nice game is pretty awesome. You have spiked my interest in Javascript canvases. The only thing I had trouble with was the jumping, sometimes it didn't work and other times it would be delayed. Overall, congratulations on your work!
Thanks! Aha, I see what you mean about the jumping - it happens when you release the space bar rather than press it. It was just easier (and more succint) to code it that way.
If you're interested in javascript and code golf, checkout the js1k compo. Some really impressive stuff. For example: https://js1k.com/2010-first/demo/635
Mind = blown. ;)