espree
An Esprima-compatible JavaScript parser built on Acorn
regexpu-core
regexpu’s core functionality (i.e. `rewritePattern(pattern, flag)`), capable of translating ES6 Unicode regular expressions to ES5.
css-tree
A tool set for CSS: fast detailed parser (CSS → AST), walker (AST traversal), generator (AST → CSS) and lexer (validation and matching) based on specs and browser implementations