I really enjoyed learning OMeta, and I'd recommend playing with it to others. However, the performance of the JavaScript implementation is really bad. It uses exceptions as a primary mechanism for control flow, which is not generally well optimized in JS. I observed a toy calculator grammar parsing a string about 20 characters long throw and catch hundreds of exceptions.

I've had good success with Jison as a JS parser generator that is performant enough to feel good about using in production.