Chevrotain

Chevrotain is a Javascript parsing DSL for building high performance fault-tolerant recursive decent parsers.

Chevrotain is NOT a parser generator. It solves the same kind of problems as a parser generator, just without any code generation phase.

---> Try it online <---

Features

1. Lexer Engine based on Regular Expression.

   • Full Token position information.
   • Token skipping (whitespace/comments/...).
   • Prioritise shorter matches (Keywords vs Identifiers).
   • Multiple Lexer Modes depending on the context.
   • Tokens Grouping
   • No code generation The Lexer does not require any code generation phase.

2. Parsing DSL for defining the grammar.

   • No code generation.
     • The DSL is just Javascript, not an external language.
     • Easily debuggable.
     • Short feedback loops.
     • Allows great flexibility for inserting custom Parser actions.
   • Error Reporting with full location information.
   • Strong Error Recovery/Fault-Tolerance capabilities based on Antlr3's algorithms.
   • Automatic lookahead calculation for LL(1) grammars.
   • Supports Custom lookahead logic for LL(k) grammars.
   • Backtracking support.

3. High performance - (see on JSPerf).

4. Grammar Reflection/Introspection.

   • The Grammar's structure is known and exposed at runtime.
   • Can be used to implement advanced features such as dynamically generated syntax diagrams or Syntactic error recovery.

5. Well tested with ~100% code coverage, Unit & Integration tests

6. Generated Railroad Diagrams.

Installation

• npm: npm install chevrotain
• Bower bower install chevrotain

Getting Started

Online tutorial

• Step #1 - Building a Lexer: online version / written version.
• Step #2 - Building a Parser: online version / written version.
• Step #3 - Adding actions to the Parser: online version / written version.
• Step #4 - Fault tolerance and Error recovery: online version / written version.

Examples Folder

Documentation

• Latest released version's HTML docs

  • Parsing DSL

• Annotated source code (dev version):

  • tokens_public.ts
  • lexer_public.ts
  • parser_public.ts
  • gast_public.ts

• The aggregated Typescript definitions :

  • chevrotain.d.ts (latest version)

Dependencies

None.

Compatibility

Chevrotain should run on any modern Javascript ES5.1 runtime.

• The CI build runs the tests under:
  • Node.js (0.12 / 4 / 5).
  • latest stable Chrome.
  • latest stable Firefox.
• Additionally local testing is done on latest versions of Chrome/Firefox/IE.
• Uses UMD to work with common module loaders (browser global / amd / commonjs).