I completed the "Tree walking interpreter" section of this book about a month ago, I used modern JS to write it and I found it a really good experience and lear

I completed the "Tree walking interpreter" section of this book about a month ago, I used modern JS to write it and I found it a really good experience and learned a fair bit. A lot of the content is obviously about implementing the interpreter so there's probably quite a bit that doesn't apply to your project, but If your looking to make your lexer as simple as possible I would recommend looking at (http://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/ http://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-e...). It's written by the same guy, and gives a short look on pratt parsers, which is one of the simplest ways to write a parser. There's also a simple language he wrote that uses the method as an example available on GitHub. At a top level you end up with declarations like: infix(token: "plus", parselet: BinaryOperator, precedence: 13); Having done a fair bit of prototyping parsers and reading about it the hardest parts of parsing JS are regex literals and automatic semi-colon insertion.