Yes, I've used Closure Compiler with advanced optimizations for the Soundslice JS codebase, for around 10 years.
It is so, so good!
You have to take care to write code in a certain way, but once you understand the constrants it's not a big deal. The advanced optimizations are better than anything else I've seen in the JS world, and it's not even close. It's just insanely good.