Keeping JavaScript from constructing high-precision timers is going to be a cat and mouse game.
See the "Fantastic Timers" paper. Link to HN discussion: https://news.ycombinator.com/item?id=16080235
See the "Fantastic Timers" paper. Link to HN discussion: https://news.ycombinator.com/item?id=16080235
The attack is already pretty damn slow (1kB/s) in C, if you have to collect a statistically significant sample in JS it might well slow down enough to not really work properly.