Created
March 30, 2012 05:17
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ES6 module loader API polyfill experiment
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(function (global) { | |
// TODO: Delegate to parent loader in various places | |
// TODO: Canonicalization | |
// TODO: Can we do better for 'eval'? | |
/// Module loader constructor | |
function Loader(parent, options) { | |
// Initialization of loader state from options | |
this._global = options.global || Object.create(null); | |
this._baseURL = options.baseURL || this.global && this.global.baseURL; | |
if (options.intrinsics === null || options.intrinsics) { | |
throw new Error("Setting 'intrinsics' not yet supported."); | |
} | |
this._strict = options.string === undefined ? false : !!options.string; | |
this._resolve = options.resolve || parent.resolve; | |
this._fetch = options.fetch || parent.fetch; | |
this._translate = options.translate || parent.translate; | |
// The internal table of module instance objects | |
this._mios = {} | |
} | |
Object.defineProperty(Loader.prototype, "global", { configurable: true, enumerable: true, get: function () { | |
return this._global; | |
}}); | |
Object.defineProperty(Loader.prototype, "baseURL", { configurable: true, enumerable: true, get: function () { | |
return this._baseURL; | |
}}); | |
Loader.prototype.load = function (url, callback, errback) { | |
var key = this._resolve(url, this._baseURL); | |
if (this._mios[key]) { | |
callback(this._mios[key]); | |
} else { | |
var self = this; | |
this._fetch(url, this._baseURL, { | |
fulfill: function (src) { | |
var actualSrc = self._translate(src, url, self._baseURL, key); | |
if (self._strict) { | |
actualSrc = "'use strict';\n" + actualSrc; | |
} | |
eval(actualSrc); | |
callback(self._mios[key]); | |
}, | |
redirect: function (url, baseURL) { | |
throw new Error("'redirect' not yet implemented"); | |
}, | |
reject: function (msg) { | |
errback(msg); | |
} | |
}, key); | |
} | |
} | |
Loader.prototype.eval = function (sourceText) { | |
with (this._global) { | |
eval(sourceText); | |
} | |
} | |
Loader.prototype.evalAsync = function () { | |
throw new Error("'evalAsync' not yet implemented. Not needed until module syntax is available."); | |
} | |
Loader.prototype.get = function (url) { | |
var key = this._resolve(url, this._baseURL); | |
return this._mios[key]; | |
} | |
Loader.prototype.set = function (url, mio) { | |
var key = this._resolve(url, this._baseURL); | |
if (typeof url == "string") { | |
this._mios[key] = Module(mio); | |
} else { | |
for (var p in key) { | |
this._mios[p] = Module(key[p]); | |
} | |
} | |
} | |
Loader.prototype.defineBuiltins = function (o) { | |
if (typeof o != "object") throw new Error("Expected object"); | |
for (var globalProp in global) { | |
o[globalProp] = global; | |
} | |
return o; | |
} | |
function Module(o) { | |
if (o == null) throw new TypeError("Expected object"); | |
var obj = Object(o); | |
if (obj instanceof Module) { | |
return obj; | |
} else { | |
var mio = Object.create(null); | |
for (var key in obj) { | |
(function(key) { | |
Object.defineProperty(mio, key, { configurable: false, enumerable: true, get: function () { | |
return obj[key]; | |
}}); | |
})(key); | |
} | |
return mio; | |
} | |
} | |
var defaultSystemLoader = new Loader(null, { | |
global: window, | |
baseURL: document.URL.substring(0, document.URL.lastIndexOf('\/') + 1), | |
strict: false, | |
resolve: function (relURL, baseURL) { | |
var url = baseURL + relURL; | |
return url; | |
}, | |
fetch: function (relURL, baseURL, request, resolved) { | |
var url = baseURL + relURL; | |
var xhr = new XMLHttpRequest(); | |
xhr.onreadystatechange = function () { | |
if (xhr.readyState === 4) { | |
if (xhr.status === 200) { | |
request.fulfill(xhr.responseText); | |
} else { | |
request.reject(xhr.statusText); | |
} | |
} | |
}; | |
xhr.open("GET", url, true); | |
xhr.send(null); | |
}, | |
translate: function (src, relURL, baseURL, resolved) { | |
return src; | |
} | |
}); | |
// Export the Loader class | |
global.Loader = Loader; | |
// Export the Module class | |
global.Module = Module; | |
// Export the System object | |
global.System = defaultSystemLoader; | |
})(this); |
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Awesome, I really like this polyfill approach. Any plans to take it further?