10 years behind? There might be competitors (perhaps) but the Closure compiler does quite a lot of impressive engineering -- not just the tree shaking and ident

10 years behind? There might be competitors (perhaps) but the Closure compiler does quite a lot of impressive engineering -- not just the tree shaking and identifier renaming that Elm is trying finally to do, but also automatic function inlining, loop unrolling, numerous other performance tweaks. And it all works fantastically, very reliable. I've been using it for 4 years on a huge codebase and I've not once had a problem that was due to the Closure compiler. It's robust and stable.