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Reflect.js is a JavaScript (ES3 compatible) implementation of Mozilla's Parser API. It does not currently support some of Mozilla's extensions, such as generators, list comprehensions, for each, E4X, etc. but may eventually support ones that are, or become Harmony proposals. Builders are also supported.

Parsing really large files can be slow, for reasons articulated by Andy Chu.


You can download a minified-standalone version of reflect.js to embed in web pages here.


Reflect.js is available as a CommonJS module for Node.js. Simply install it with npm:

npm install reflect


var Reflect = require('reflect');

var ast = Reflect.parse("var a = 4 + 7");

console.log(Reflect.stringify(ast, "  "));

Refer to Mozilla's docs for details on the AST interface.


The optional builder parameter to Reflect.parse() makes it possible to construct user-specified data from the parser, rather than the default Node objects.

The reflect.js module exports the default builder so you can redefine only the node constructors you care about and leave the rest default.

var Reflect = require('reflect');
var builder = Reflect.builder;

// redefine callback for variable declarations
builder["variableDeclaration"] = function (kind, declarators, loc) { ... };

var ast = Reflect.parse("var a = 4 + 7", {builder: builder});


MIT X Licensed.