PEG.js is a simple parser generator for JavaScript that produces fast parsers with excellent error reporting. You can use it to process complex data or computer languages and build transformers, interpreters, compilers and other tools easily.


  • Simple and expressive grammar syntax
  • Integrates both lexical and syntactical analysis
  • Parsers have excellent error reporting out of the box
  • Based on parsing expression grammar formalism — more powerful than traditional LL(k) and LR(k) parsers
  • Usable from your browser, from the command line, or via JavaScript API