There are two JavaScript browsers that exist, Google Chromium forks and Mozilla Firefox forks. Neither is good. It is impossible to write a good JavaScript browser because the world of JavaScript is so big and keeps changing so often (not to mention the security considerations of downloading arbitrary programs from the web and running them on your computer) that you can't keep up without a full-time development team who need to be paid. The entire webdev world seems extremely unsustainable and I really wish everyone took going back to a simpler web more seriously (but obviously they won't).

@vaporeon_ webkit also exists but i don’t really think that matters fur the point you’re actually making