Seafox
A blazing fast 100% spec compliant, self-hosted javascript parser written in Typescript.
Features
- Conforms to the standard ECMAScript® 2021 (ECMA-262 11th Edition) language specification
- Support for additional ECMAScript features for Web Browsers
- Optionally track syntactic node locations
- Emits an ESTree-compatible abstract syntax tree
- Lexical analysis
- No backtracking
- Low memory usage
- Insane performance both on desktop computers and handheld devices
- Twice as fast as other Javascript parsers
- Very well tested (~33 000 unit tests with full code coverage)
- Lightweight - ~84 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) or lexical analysis (tokenization) of a JavaScript program, and with ES2015
and later a JavaScript program can be either a script or a module.
The parse
method exposed by Seafox
takes an optional options
object which allows you to specify whether to parse in script
mode (the default) or in module
mode.
This is the available options:
// Allow parsing using Module as the goal symbol module?: boolean; // 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; // Allows token extraction. Accepts only a function {}
Example usage:
; parseScript'({x: [y] = 0} = 1)'; parseModule'({x: [y] = 0} = 1)', ; parse'({x: [y] = 0} = 1)', ; parse'({x: [y] = 0} = 1)';
Lexical analysis
Lexical analysis can only be done during parsing and accepts only a function type as the option
parseScript'foo = bar', ;
The callback function have 4 arguments.
Arguments | Description |
---|---|
token |
The token to be extracted |
value |
Value of the extracted token |
start |
Start position of the extracted token |
end |
End position of the extracted token |
The loc
option needs to be enabled for start
and end
. Otherwise this values will be set to undefined
Performance
Seafox is developed for performance and low memory usage, and the parser is about 2x - 4x faster than all other javascript parsers.