Seafox

A blazing fast 100% spec compliant, self-hosted javascript parser written in Typescript.

Features

• Conforms to the standard ECMAScript® 2020 (ECMA-262 10th Edition) language specification
• Support for additional ECMAScript features for Web Browsers
• Optionally track syntactic node locations
• Emits an ESTree-compatible abstract syntax tree.
• No backtracking
• Low memory usage
• Very well tested (~30 000 unit tests with full code coverage)
• Lightweight - ~87 KB minified

Installation

npm install seafox --save-dev

API

Seafox generates AST according to ESTree AST format, and can be used to perform syntactic analysis (parsing) of a JavaScript program, and with ES2015 and later a JavaScript program can be either a script or a module.

Seafox stricly follows the ECMA specifications so you have to specify whether to parse in parseScript mode (the default) or in parseModule mode.

This is the available options:

{
  // The flag to enable start and end offsets and line/column location information to each node
  loc: false;

  // Disable web compatibility
  disableWebCompat: false;

  // The flag to attach raw property to each literal and identifier node
  raw: false;

  // Enabled directives
  directives: false;

  // The flag to allow return in the global scope
  globalReturn: false;

  // The flag to enable implied strict mode
  impliedStrict: false;

// Enable non-standard parenthesized expression node
  preserveParens: false;
}

Example usage:

import { parseScript, parseModule } from './seafox';

parseScript('({x: [y] = 0} = 1)');

parseModule('({x: [y] = 0} = 1)', { directives: true, raw: true });

What is Seafox?

This is my private parser code made public. It strictly conforms to the standard ECMAScript® 2020 (ECMA-262 10th Edition) language specification, and can not be used as an drop-in replacement for other parsers, because they are using a parse() method as an common public API to parse javascript code.

Seafox uses either parseScript or parseModule.

The main focus for Seafox is performance, and if you are soft hearted and / or can't understand super low level code - this parser isn't for you :)

I would recommend to use the Meriyah parser instead of Seafox if you need a parser that behave like other public parsers, and also if you are in need of performance even the fact that Seafox is 15 - 25 % faster than the mentioned parser.