xgrommx/harmony-reflect

ES-Harmony reflect module shim

This is a shim for the ECMAScript 6 reflection module.

In a browser, after loading

<script src="reflect.js"></script>

a global object Reflect is defined that contains the functions from the ES6 reflect module (see below).

The Proxy object is also updated to follow the latest direct proxies spec. To create such a proxy, call:

var proxy = Proxy(target, handler)

If you are using node.js (>= v0.7.8), you can install via npm:

npm install harmony-reflect

Then:

node --harmony
> require('harmony-reflect');

API

This module exports a single object named Reflect.

The ECMAScript 6 Proxy API allows one to intercept various operations on Javascript objects.

• Overview of all supported traps on proxies
• The Reflect API
• The Proxy Handler API

Compatibility

The Reflect API, with support for proxies, was tested on:

• Firefox 12 (should work since Firefox 4)
• Chrome 19, under an experimental flag
• spidermonkey shell
• v8 --harmony (on 3.11.0, should work since at least v3.6)
• node --harmony (in node v0.7.8)

Dependencies

• ECMAScript 5/strict
• To emulate direct proxies: * old Harmony Proxies * Harmony WeakMaps

After loading reflect.js into your page or other JS environment, be aware that the following globals are patched to be able to recognize emulated direct proxies:

Object.{freeze,seal,preventExtensions}
Object.{isFrozen,isSealed,isExtensible}
Object.getPrototypeOf
Object.prototype.valueOf
Object.getOwnPropertyDescriptor
Object.defineProperty
Function.prototype.toString
Date.prototype.toString
Array.isArray
Array.prototype.concat
Proxy

Examples

The examples directory contains a number of examples demonstrating the use of proxies:

• membranes: wrappers that transitively isolate two object-graphs.
• observer: a self-hosted implementation of the ES7 Object.observe notification mechanism.
• profiler: a simple profiler to collect usage statistics of an object.

Spec Compatibility

This library differs from the draft ECMAScript 6 spec. as follows:

• No support yet for the invoke() trap on proxies.
• Still includes seal() and freeze() as traps on proxies and methods in Reflect (ES6 removed them, i.e. calling Object.seal(proxy) will instead trigger other traps on the proxy, such as defineProperty and preventExtensions).
• Array.isArray(obj) and [].concat(obj) are patched so they work transparently on proxies-for-arrays (e.g. when obj is new Proxy([],{})). It is as yet unclear how ES6 will spec these operations in the presence of proxies.