This confused me quite a bit as well. "Wait, what? There's such a thing as a blocking quicksort? Maybe with mutexes or something, but this is JavaScript..."

This confused me quite a bit as well. "Wait, what? There's such a thing as a blocking quicksort? Maybe with mutexes or something, but this is JavaScript..." Apparently "non-blocking" is used here to mean roughly the opposite of what it normally means (that your computation doesn't slow down the I/O). Oddly enough, this seems kind of reasonable for interactive programs: the I/O is the more important part, so it's the thing you want to not interfere with. It's still a little confusing.