Nitpicking certainly but I would say use something like antlr rather than peg.js

antlr "schemas" are extremely close to ebnf's (some exceptions obviously) and the compiler creation club could benefit from that. Antlr 3 is usable in a variaty of languages (although 4 is a hellavalot simpler and solves a fair bit around left recursive grammers, but non jvm support is non existent still I suspect)