They're all prototypes illustrating better security architectures. Such work often doesn't have all functionality included. Nonetheless, these support JavaScript: OP1 & OP2 web browsers; Microsoft's Gazelle; Tahoma; IBOS; my two kludge solutions I mentioned. So, all of them except the DARPAbrowser which was just a demo for Combex's methods. Papers below on on their architectures, security analysis, and performance evaluation if you're interested.

Far from "use it now," I'm advocating that they illustrate the difference between strong security design and mainstream while providing something to build on. My claim is building on stuff like this would reduce impact of hackers vs popular browsers. Many trusted components can also be built to medium or high assurance because they're simpler.

DARPAbrowser demo http://www.combex.com/tech/darpaBrowser.html

Designing and Implementing the OP and OP2 Web Browsers http://web.engr.illinois.edu/~kingst/Research_files/grier11....

Multi-principal OS Construction of Gazelle Web Browser http://research.microsoft.com/pubs/79655/gazelle.pdf

Tahoma - A Safety-oriented Platform for Web Applications http://homes.cs.washington.edu/~gribble/papers/gribble-Tahom...

Trust and Protection in the Illinois Browser Operating System https://www.usenix.org/legacy/events/osdi10/tech/full_papers...