Do you realize that in Canvas colors are represented as a "series of text strings" that need to be parsed?

Did you know that drawing paths requires a ton of pretty expensive Javascript calls or alternatively passing "a series of text strings"? Maybe the string way is actually faster, I haven't tested it because it isn't supported everywhere.

Were you aware that vector rendering is not usually done on GPUs, mainly because of the high overhead of state changes when using a graphics API, especially one like WebGL?

I guess you could do all your rendering in software in Javascript (which for these purposes is nowhere close to what you can get with C/C++) to a byte buffer and then do the final transfer to Canvas. Even in that case, you might be surprised how much overhead that final transfer has...