es5-shim.js

// vim: ts=4 sts=4 sw=4 expandtab
// -- kriskowal Kris Kowal Copyright (C) 2009-2011 MIT License
// -- tlrobinson Tom Robinson Copyright (C) 2009-2010 MIT License (Narwhal Project)
// -- dantman Daniel Friesen Copyright (C) 2010 XXX TODO License or CLA
// -- fschaefer Florian Schäfer Copyright (C) 2010 MIT License
// -- Gozala Irakli Gozalishvili Copyright (C) 2010 MIT License
// -- kitcambridge Kit Cambridge Copyright (C) 2011 MIT License
// -- kossnocorp Sasha Koss XXX TODO License or CLA
// -- bryanforbes Bryan Forbes XXX TODO License or CLA
// -- killdream Quildreen Motta Copyright (C) 2011 MIT Licence
// -- michaelficarra Michael Ficarra Copyright (C) 2011 3-clause BSD License
// -- sharkbrainguy Gerard Paapu Copyright (C) 2011 MIT License
// -- bbqsrc Brendan Molloy (C) 2011 Creative Commons Zero (public domain)
// -- iwyg XXX TODO License or CLA
// -- DomenicDenicola Domenic Denicola Copyright (C) 2011 MIT License
// -- xavierm02 Montillet Xavier Copyright (C) 2011 MIT License
// -- Raynos Jake Verbaten Copyright (C) 2011 MIT Licence
// -- samsonjs Sami Samhuri Copyright (C) 2010 MIT License
// -- rwldrn Rick Waldron Copyright (C) 2011 MIT License
// -- lexer Alexey Zakharov XXX TODO License or CLA

/*!
    Copyright (c) 2009, 280 North Inc. http://280north.com/
    MIT License. http://github.com/280north/narwhal/blob/master/README.md
*/

// Module systems magic dance
(function (definition) {
    // RequireJS
    if (typeof define == "function") {
        define(definition);
    // CommonJS and <script>
    } else {
        definition();
    }
})(function () {

/**
 * Brings an environment as close to ECMAScript 5 compliance
 * as is possible with the facilities of erstwhile engines.
 *
 * Annotated ES5: http://es5.github.com/ (specific links below)
 * ES5 Spec: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf
 * Required reading: http://javascriptweblog.wordpress.com/2011/12/05/extending-javascript-natives/
 */

//
// Function
// ========
//

// ES-5 15.3.4.5
// http://es5.github.com/#x15.3.4.5

if (!Function.prototype.bind) {
    Function.prototype.bind = function bind(that) { // .length is 1
        // 1. Let Target be the this value.
        var target = this;
        // 2. If IsCallable(Target) is false, throw a TypeError exception.
        if (typeof target != "function") {
            throw new TypeError("Function.prototype.bind called on incompatible " + target);
        }
        // 3. Let A be a new (possibly empty) internal list of all of the
        //   argument values provided after thisArg (arg1, arg2 etc), in order.
        // XXX slicedArgs will stand in for "A" if used
        var args = slice.call(arguments, 1); // for normal call
        // 4. Let F be a new native ECMAScript object.
        // 11. Set the [[Prototype]] internal property of F to the standard
        //   built-in Function prototype object as specified in 15.3.3.1.
        // 12. Set the [[Call]] internal property of F as described in
        //   15.3.4.5.1.
        // 13. Set the [[Construct]] internal property of F as described in
        //   15.3.4.5.2.
        // 14. Set the [[HasInstance]] internal property of F as described in
        //   15.3.4.5.3.
        var bound = function () {

            if (this instanceof bound) {
                // 15.3.4.5.2 [[Construct]]
                // When the [[Construct]] internal method of a function object,
                // F that was created using the bind function is called with a
                // list of arguments ExtraArgs, the following steps are taken:
                // 1. Let target be the value of F's [[TargetFunction]]
                //   internal property.
                // 2. If target has no [[Construct]] internal method, a
                //   TypeError exception is thrown.
                // 3. Let boundArgs be the value of F's [[BoundArgs]] internal
                //   property.
                // 4. Let args be a new list containing the same values as the
                //   list boundArgs in the same order followed by the same
                //   values as the list ExtraArgs in the same order.
                // 5. Return the result of calling the [[Construct]] internal
                //   method of target providing args as the arguments.

                var F = function(){};
                F.prototype = target.prototype;
                var self = new F;

                var result = target.apply(
                    self,
                    args.concat(slice.call(arguments))
                );
                if (Object(result) === result) {
                    return result;
                }
                return self;

            } else {
                // 15.3.4.5.1 [[Call]]
                // When the [[Call]] internal method of a function object, F,
                // which was created using the bind function is called with a
                // this value and a list of arguments ExtraArgs, the following
                // steps are taken:
                // 1. Let boundArgs be the value of F's [[BoundArgs]] internal
                //   property.
                // 2. Let boundThis be the value of F's [[BoundThis]] internal
                //   property.
                // 3. Let target be the value of F's [[TargetFunction]] internal
                //   property.
                // 4. Let args be a new list containing the same values as the
                //   list boundArgs in the same order followed by the same
                //   values as the list ExtraArgs in the same order.
                // 5. Return the result of calling the [[Call]] internal method
                //   of target providing boundThis as the this value and
                //   providing args as the arguments.

                // equiv: target.call(this, ...boundArgs, ...args)
                return target.apply(
                    that,
                    args.concat(slice.call(arguments))
                );

            }

        };
        // XXX bound.length is never writable, so don't even try
        //
        // 15. If the [[Class]] internal property of Target is "Function", then
        //     a. Let L be the length property of Target minus the length of A.
        //     b. Set the length own property of F to either 0 or L, whichever is
        //       larger.
        // 16. Else set the length own property of F to 0.
        // 17. Set the attributes of the length own property of F to the values
        //   specified in 15.3.5.1.

        // TODO
        // 18. Set the [[Extensible]] internal property of F to true.

        // TODO
        // 19. Let thrower be the [[ThrowTypeError]] function Object (13.2.3).
        // 20. Call the [[DefineOwnProperty]] internal method of F with
        //   arguments "caller", PropertyDescriptor {[[Get]]: thrower, [[Set]]:
        //   thrower, [[Enumerable]]: false, [[Configurable]]: false}, and
        //   false.
        // 21. Call the [[DefineOwnProperty]] internal method of F with
        //   arguments "arguments", PropertyDescriptor {[[Get]]: thrower,
        //   [[Set]]: thrower, [[Enumerable]]: false, [[Configurable]]: false},
        //   and false.

        // TODO
        // NOTE Function objects created using Function.prototype.bind do not
        // have a prototype property or the [[Code]], [[FormalParameters]], and
        // [[Scope]] internal properties.
        // XXX can't delete prototype in pure-js.

        // 22. Return F.
        return bound;
    };
}

// Shortcut to an often accessed properties, in order to avoid multiple
// dereference that costs universally.
// _Please note: Shortcuts are defined after `Function.prototype.bind` as we
// us it in defining shortcuts.
var call = Function.prototype.call;
var prototypeOfArray = Array.prototype;
var prototypeOfObject = Object.prototype;
var slice = prototypeOfArray.slice;
// Having a toString local variable name breaks in Opera so use _toString.
var _toString = call.bind(prototypeOfObject.toString);
var owns = call.bind(prototypeOfObject.hasOwnProperty);

// If JS engine supports accessors creating shortcuts.
var defineGetter;
var defineSetter;
var lookupGetter;
var lookupSetter;
var supportsAccessors;
if ((supportsAccessors = owns(prototypeOfObject, "__defineGetter__"))) {
    defineGetter = call.bind(prototypeOfObject.__defineGetter__);
    defineSetter = call.bind(prototypeOfObject.__defineSetter__);
    lookupGetter = call.bind(prototypeOfObject.__lookupGetter__);
    lookupSetter = call.bind(prototypeOfObject.__lookupSetter__);
}

//
// Array
// =====
//

// ES5 15.4.3.2
// http://es5.github.com/#x15.4.3.2
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/isArray
if (!Array.isArray) {
    Array.isArray = function isArray(obj) {
        return _toString(obj) == "[object Array]";
    };
}

// The IsCallable() check in the Array functions
// has been replaced with a strict check on the
// internal class of the object to trap cases where
// the provided function was actually a regular
// expression literal, which in V8 and
// JavaScriptCore is a typeof "function".  Only in
// V8 are regular expression literals permitted as
// reduce parameters, so it is desirable in the
// general case for the shim to match the more
// strict and common behavior of rejecting regular
// expressions.

// ES5 15.4.4.18
// http://es5.github.com/#x15.4.4.18
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/array/forEach
if (!Array.prototype.forEach) {
    Array.prototype.forEach = function forEach(fun /*, thisp*/) {
        var self = toObject(this),
            thisp = arguments[1],
            i = -1,
            length = self.length >>> 0;

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(); // TODO message
        }

        while (++i < length) {
            if (i in self) {
                // Invoke the callback function with call, passing arguments:
                // context, property value, property key, thisArg object context
                fun.call(thisp, self[i], i, self);
            }
        }
    };
}

// ES5 15.4.4.19
// http://es5.github.com/#x15.4.4.19
// https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/map
if (!Array.prototype.map) {
    Array.prototype.map = function map(fun /*, thisp*/) {
        var self = toObject(this),
            length = self.length >>> 0,
            result = Array(length),
            thisp = arguments[1];

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        for (var i = 0; i < length; i++) {
            if (i in self)
                result[i] = fun.call(thisp, self[i], i, self);
        }
        return result;
    };
}

// ES5 15.4.4.20
// http://es5.github.com/#x15.4.4.20
// https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/filter
if (!Array.prototype.filter) {
    Array.prototype.filter = function filter(fun /*, thisp */) {
        var self = toObject(this),
            length = self.length >>> 0,
            result = [],
            value,
            thisp = arguments[1];

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        for (var i = 0; i < length; i++) {
            if (i in self) {
                value = self[i];
                if (fun.call(thisp, value, i, self)) {
                    result.push(value);
                }
            }
        }
        return result;
    };
}

// ES5 15.4.4.16
// http://es5.github.com/#x15.4.4.16
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/every
if (!Array.prototype.every) {
    Array.prototype.every = function every(fun /*, thisp */) {
        var self = toObject(this),
            length = self.length >>> 0,
            thisp = arguments[1];

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        for (var i = 0; i < length; i++) {
            if (i in self && !fun.call(thisp, self[i], i, self)) {
                return false;
            }
        }
        return true;
    };
}

// ES5 15.4.4.17
// http://es5.github.com/#x15.4.4.17
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/some
if (!Array.prototype.some) {
    Array.prototype.some = function some(fun /*, thisp */) {
        var self = toObject(this),
            length = self.length >>> 0,
            thisp = arguments[1];

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        for (var i = 0; i < length; i++) {
            if (i in self && fun.call(thisp, self[i], i, self)) {
                return true;
            }
        }
        return false;
    };
}

// ES5 15.4.4.21
// http://es5.github.com/#x15.4.4.21
// https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/reduce
if (!Array.prototype.reduce) {
    Array.prototype.reduce = function reduce(fun /*, initial*/) {
        var self = toObject(this),
            length = self.length >>> 0;

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        // no value to return if no initial value and an empty array
        if (!length && arguments.length == 1) {
            throw new TypeError('reduce of empty array with no initial value');
        }

        var i = 0;
        var result;
        if (arguments.length >= 2) {
            result = arguments[1];
        } else {
            do {
                if (i in self) {
                    result = self[i++];
                    break;
                }

                // if array contains no values, no initial value to return
                if (++i >= length) {
                    throw new TypeError('reduce of empty array with no initial value');
                }
            } while (true);
        }

        for (; i < length; i++) {
            if (i in self) {
                result = fun.call(void 0, result, self[i], i, self);
            }
        }

        return result;
    };
}

// ES5 15.4.4.22
// http://es5.github.com/#x15.4.4.22
// https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/reduceRight
if (!Array.prototype.reduceRight) {
    Array.prototype.reduceRight = function reduceRight(fun /*, initial*/) {
        var self = toObject(this),
            length = self.length >>> 0;

        // If no callback function or if callback is not a callable function
        if (_toString(fun) != "[object Function]") {
            throw new TypeError(fun + " is not a function");
        }

        // no value to return if no initial value, empty array
        if (!length && arguments.length == 1) {
            throw new TypeError('reduceRight of empty array with no initial value');
        }

        var result, i = length - 1;
        if (arguments.length >= 2) {
            result = arguments[1];
        } else {
            do {
                if (i in self) {
                    result = self[i--];
                    break;
                }

                // if array contains no values, no initial value to return
                if (--i < 0) {
                    throw new TypeError('reduceRight of empty array with no initial value');
                }
            } while (true);
        }

        do {
            if (i in this) {
                result = fun.call(void 0, result, self[i], i, self);
            }
        } while (i--);

        return result;
    };
}

// ES5 15.4.4.14
// http://es5.github.com/#x15.4.4.14
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/indexOf
if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function indexOf(sought /*, fromIndex */ ) {
        var self = toObject(this),
            length = self.length >>> 0;

        if (!length) {
            return -1;
        }

        var i = 0;
        if (arguments.length > 1) {
            i = toInteger(arguments[1]);
        }

        // handle negative indices
        i = i >= 0 ? i : Math.max(0, length + i);
        for (; i < length; i++) {
            if (i in self && self[i] === sought) {
                return i;
            }
        }
        return -1;
    };
}

// ES5 15.4.4.15
// http://es5.github.com/#x15.4.4.15
// https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/lastIndexOf
if (!Array.prototype.lastIndexOf) {
    Array.prototype.lastIndexOf = function lastIndexOf(sought /*, fromIndex */) {
        var self = toObject(this),
            length = self.length >>> 0;

        if (!length) {
            return -1;
        }
        var i = length - 1;
        if (arguments.length > 1) {
            i = Math.min(i, toInteger(arguments[1]));
        }
        // handle negative indices
        i = i >= 0 ? i : length - Math.abs(i);
        for (; i >= 0; i--) {
            if (i in self && sought === self[i]) {
                return i;
            }
        }
        return -1;
    };
}

//
// Object
// ======
//

// ES5 15.2.3.2
// http://es5.github.com/#x15.2.3.2
if (!Object.getPrototypeOf) {
    // https://github.com/kriskowal/es5-shim/issues#issue/2
    // http://ejohn.org/blog/objectgetprototypeof/
    // recommended by fschaefer on github
    Object.getPrototypeOf = function getPrototypeOf(object) {
        return object.__proto__ || (
            object.constructor
                ? object.constructor.prototype
                : prototypeOfObject
        );
    };
}

// ES5 15.2.3.3
// http://es5.github.com/#x15.2.3.3
if (!Object.getOwnPropertyDescriptor) {
    var ERR_NON_OBJECT = "Object.getOwnPropertyDescriptor called on a non-object: ";

    Object.getOwnPropertyDescriptor = function getOwnPropertyDescriptor(object, property) {
        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError(ERR_NON_OBJECT + object);
        }
        // If object does not owns property return undefined immediately.
        if (!owns(object, property)) {
            return;
        }

        // If object has a property then it's for sure both `enumerable` and
        // `configurable`.
        var descriptor =  { enumerable: true, configurable: true };

        // If JS engine supports accessor properties then property may be a
        // getter or setter.
        if (supportsAccessors) {
            // Unfortunately `__lookupGetter__` will return a getter even
            // if object has own non getter property along with a same named
            // inherited getter. To avoid misbehavior we temporary remove
            // `__proto__` so that `__lookupGetter__` will return getter only
            // if it's owned by an object.
            var prototype = object.__proto__;
            object.__proto__ = prototypeOfObject;

            var getter = lookupGetter(object, property);
            var setter = lookupSetter(object, property);

            // Once we have getter and setter we can put values back.
            object.__proto__ = prototype;

            if (getter || setter) {
                if (getter) {
                    descriptor.get = getter;
                }
                if (setter) {
                    descriptor.set = setter;
                }
                // If it was accessor property we're done and return here
                // in order to avoid adding `value` to the descriptor.
                return descriptor;
            }
        }

        // If we got this far we know that object has an own property that is
        // not an accessor so we set it as a value and return descriptor.
        descriptor.value = object[property];
        return descriptor;
    };
}

// ES5 15.2.3.4
// http://es5.github.com/#x15.2.3.4
if (!Object.getOwnPropertyNames) {
    Object.getOwnPropertyNames = function getOwnPropertyNames(object) {
        return Object.keys(object);
    };
}

// ES5 15.2.3.5
// http://es5.github.com/#x15.2.3.5
if (!Object.create) {
    Object.create = function create(prototype, properties) {
        var object;
        if (prototype === null) {
            object = { "__proto__": null };
        } else {
            if (typeof prototype != "object") {
                throw new TypeError("typeof prototype["+(typeof prototype)+"] != 'object'");
            }
            var Type = function () {};
            Type.prototype = prototype;
            object = new Type();
            // IE has no built-in implementation of `Object.getPrototypeOf`
            // neither `__proto__`, but this manually setting `__proto__` will
            // guarantee that `Object.getPrototypeOf` will work as expected with
            // objects created using `Object.create`
            object.__proto__ = prototype;
        }
        if (properties !== void 0) {
            Object.defineProperties(object, properties);
        }
        return object;
    };
}

// ES5 15.2.3.6
// http://es5.github.com/#x15.2.3.6

// Patch for WebKit and IE8 standard mode
// Designed by hax <hax.github.com>
// related issue: https://github.com/kriskowal/es5-shim/issues#issue/5
// IE8 Reference:
//     http://msdn.microsoft.com/en-us/library/dd282900.aspx
//     http://msdn.microsoft.com/en-us/library/dd229916.aspx
// WebKit Bugs:
//     https://bugs.webkit.org/show_bug.cgi?id=36423

function doesDefinePropertyWork(object) {
    try {
        Object.defineProperty(object, "sentinel", {});
        return "sentinel" in object;
    } catch (exception) {
        // returns falsy
    }
}

// check whether defineProperty works if it's given. Otherwise,
// shim partially.
if (Object.defineProperty) {
    var definePropertyWorksOnObject = doesDefinePropertyWork({});
    var definePropertyWorksOnDom = typeof document == "undefined" ||
        doesDefinePropertyWork(document.createElement("div"));
    if (!definePropertyWorksOnObject || !definePropertyWorksOnDom) {
        var definePropertyFallback = Object.defineProperty;
    }
}

if (!Object.defineProperty || definePropertyFallback) {
    var ERR_NON_OBJECT_DESCRIPTOR = "Property description must be an object: ";
    var ERR_NON_OBJECT_TARGET = "Object.defineProperty called on non-object: "
    var ERR_ACCESSORS_NOT_SUPPORTED = "getters & setters can not be defined " +
                                      "on this javascript engine";

    Object.defineProperty = function defineProperty(object, property, descriptor) {
        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError(ERR_NON_OBJECT_TARGET + object);
        }
        if ((typeof descriptor != "object" && typeof descriptor != "function") || descriptor === null) {
            throw new TypeError(ERR_NON_OBJECT_DESCRIPTOR + descriptor);
        }
        // make a valiant attempt to use the real defineProperty
        // for I8's DOM elements.
        if (definePropertyFallback) {
            try {
                return definePropertyFallback.call(Object, object, property, descriptor);
            } catch (exception) {
                // try the shim if the real one doesn't work
            }
        }

        // If it's a data property.
        if (owns(descriptor, "value")) {
            // fail silently if "writable", "enumerable", or "configurable"
            // are requested but not supported
            /*
            // alternate approach:
            if ( // can't implement these features; allow false but not true
                !(owns(descriptor, "writable") ? descriptor.writable : true) ||
                !(owns(descriptor, "enumerable") ? descriptor.enumerable : true) ||
                !(owns(descriptor, "configurable") ? descriptor.configurable : true)
            )
                throw new RangeError(
                    "This implementation of Object.defineProperty does not " +
                    "support configurable, enumerable, or writable."
                );
            */

            if (supportsAccessors && (lookupGetter(object, property) ||
                                      lookupSetter(object, property)))
            {
                // As accessors are supported only on engines implementing
                // `__proto__` we can safely override `__proto__` while defining
                // a property to make sure that we don't hit an inherited
                // accessor.
                var prototype = object.__proto__;
                object.__proto__ = prototypeOfObject;
                // Deleting a property anyway since getter / setter may be
                // defined on object itself.
                delete object[property];
                object[property] = descriptor.value;
                // Setting original `__proto__` back now.
                object.__proto__ = prototype;
            } else {
                object[property] = descriptor.value;
            }
        } else {
            if (!supportsAccessors) {
                throw new TypeError(ERR_ACCESSORS_NOT_SUPPORTED);
            }
            // If we got that far then getters and setters can be defined !!
            if (owns(descriptor, "get")) {
                defineGetter(object, property, descriptor.get);
            }
            if (owns(descriptor, "set")) {
                defineSetter(object, property, descriptor.set);
            }
        }
        return object;
    };
}

// ES5 15.2.3.7
// http://es5.github.com/#x15.2.3.7
if (!Object.defineProperties) {
    Object.defineProperties = function defineProperties(object, properties) {
        for (var property in properties) {
            if (owns(properties, property) && property != "__proto__") {
                Object.defineProperty(object, property, properties[property]);
            }
        }
        return object;
    };
}

// ES5 15.2.3.8
// http://es5.github.com/#x15.2.3.8
if (!Object.seal) {
    Object.seal = function seal(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// ES5 15.2.3.9
// http://es5.github.com/#x15.2.3.9
if (!Object.freeze) {
    Object.freeze = function freeze(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// detect a Rhino bug and patch it
try {
    Object.freeze(function () {});
} catch (exception) {
    Object.freeze = (function freeze(freezeObject) {
        return function freeze(object) {
            if (typeof object == "function") {
                return object;
            } else {
                return freezeObject(object);
            }
        };
    })(Object.freeze);
}

// ES5 15.2.3.10
// http://es5.github.com/#x15.2.3.10
if (!Object.preventExtensions) {
    Object.preventExtensions = function preventExtensions(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// ES5 15.2.3.11
// http://es5.github.com/#x15.2.3.11
if (!Object.isSealed) {
    Object.isSealed = function isSealed(object) {
        return false;
    };
}

// ES5 15.2.3.12
// http://es5.github.com/#x15.2.3.12
if (!Object.isFrozen) {
    Object.isFrozen = function isFrozen(object) {
        return false;
    };
}

// ES5 15.2.3.13
// http://es5.github.com/#x15.2.3.13
if (!Object.isExtensible) {
    Object.isExtensible = function isExtensible(object) {
        // 1. If Type(O) is not Object throw a TypeError exception.
        if (Object(object) !== object) {
            throw new TypeError(); // TODO message
        }
        // 2. Return the Boolean value of the [[Extensible]] internal property of O.
        var name = '';
        while (owns(object, name)) {
            name += '?';
        }
        object[name] = true;
        var returnValue = owns(object, name);
        delete object[name];
        return returnValue;
    };
}

// ES5 15.2.3.14
// http://es5.github.com/#x15.2.3.14
if (!Object.keys) {
    // http://whattheheadsaid.com/2010/10/a-safer-object-keys-compatibility-implementation
    var hasDontEnumBug = true,
        dontEnums = [
            "toString",
            "toLocaleString",
            "valueOf",
            "hasOwnProperty",
            "isPrototypeOf",
            "propertyIsEnumerable",
            "constructor"
        ],
        dontEnumsLength = dontEnums.length;

    for (var key in {"toString": null}) {
        hasDontEnumBug = false;
    }

    Object.keys = function keys(object) {

        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError("Object.keys called on a non-object");
        }

        var keys = [];
        for (var name in object) {
            if (owns(object, name)) {
                keys.push(name);
            }
        }

        if (hasDontEnumBug) {
            for (var i = 0, ii = dontEnumsLength; i < ii; i++) {
                var dontEnum = dontEnums[i];
                if (owns(object, dontEnum)) {
                    keys.push(dontEnum);
                }
            }
        }
        return keys;
    };

}

//
// Date
// ====
//

// ES5 15.9.5.43
// http://es5.github.com/#x15.9.5.43
// This function returns a String value represent the instance in time
// represented by this Date object. The format of the String is the Date Time
// string format defined in 15.9.1.15. All fields are present in the String.
// The time zone is always UTC, denoted by the suffix Z. If the time value of
// this object is not a finite Number a RangeError exception is thrown.
if (!Date.prototype.toISOString || (new Date(-62198755200000).toISOString().indexOf('-000001') === -1)) {
    Date.prototype.toISOString = function toISOString() {
        var result, length, value, year;
        if (!isFinite(this)) {
            throw new RangeError("Date.prototype.toISOString called on non-finite value.");
        }

        // the date time string format is specified in 15.9.1.15.
        result = [this.getUTCMonth() + 1, this.getUTCDate(),
            this.getUTCHours(), this.getUTCMinutes(), this.getUTCSeconds()];
        year = this.getUTCFullYear();
        year = (year < 0 ? '-' : (year > 9999 ? '+' : '')) + ('00000' + Math.abs(year)).slice(0 <= year && year <= 9999 ? -4 : -6);

        length = result.length;
        while (length--) {
            value = result[length];
            // pad months, days, hours, minutes, and seconds to have two digits.
            if (value < 10) {
                result[length] = "0" + value;
            }
        }
        // pad milliseconds to have three digits.
        return year + "-" + result.slice(0, 2).join("-") + "T" + result.slice(2).join(":") + "." +
            ("000" + this.getUTCMilliseconds()).slice(-3) + "Z";
    }
}

// ES5 15.9.4.4
// http://es5.github.com/#x15.9.4.4
if (!Date.now) {
    Date.now = function now() {
        return new Date().getTime();
    };
}

// ES5 15.9.5.44
// http://es5.github.com/#x15.9.5.44
// This function provides a String representation of a Date object for use by
// JSON.stringify (15.12.3).
if (!Date.prototype.toJSON) {
    Date.prototype.toJSON = function toJSON(key) {
        // When the toJSON method is called with argument key, the following
        // steps are taken:

        // 1.  Let O be the result of calling ToObject, giving it the this
        // value as its argument.
        // 2. Let tv be ToPrimitive(O, hint Number).
        // 3. If tv is a Number and is not finite, return null.
        // XXX
        // 4. Let toISO be the result of calling the [[Get]] internal method of
        // O with argument "toISOString".
        // 5. If IsCallable(toISO) is false, throw a TypeError exception.
        if (typeof this.toISOString != "function") {
            throw new TypeError('toISOString property is not callable');
        }
        // 6. Return the result of calling the [[Call]] internal method of
        //  toISO with O as the this value and an empty argument list.
        return this.toISOString();

        // NOTE 1 The argument is ignored.

        // NOTE 2 The toJSON function is intentionally generic; it does not
        // require that its this value be a Date object. Therefore, it can be
        // transferred to other kinds of objects for use as a method. However,
        // it does require that any such object have a toISOString method. An
        // object is free to use the argument key to filter its
        // stringification.
    };
}

// ES5 15.9.4.2
// http://es5.github.com/#x15.9.4.2
// based on work shared by Daniel Friesen (dantman)
// http://gist.github.com/303249
if (!Date.parse || Date.parse("+275760-09-13T00:00:00.000Z") !== 8.64e15) {
    // XXX global assignment won't work in embeddings that use
    // an alternate object for the context.
    Date = (function(NativeDate) {

        // Date.length === 7
        var Date = function Date(Y, M, D, h, m, s, ms) {
            var length = arguments.length;
            if (this instanceof NativeDate) {
                var date = length == 1 && String(Y) === Y ? // isString(Y)
                    // We explicitly pass it through parse:
                    new NativeDate(Date.parse(Y)) :
                    // We have to manually make calls depending on argument
                    // length here
                    length >= 7 ? new NativeDate(Y, M, D, h, m, s, ms) :
                    length >= 6 ? new NativeDate(Y, M, D, h, m, s) :
                    length >= 5 ? new NativeDate(Y, M, D, h, m) :
                    length >= 4 ? new NativeDate(Y, M, D, h) :
                    length >= 3 ? new NativeDate(Y, M, D) :
                    length >= 2 ? new NativeDate(Y, M) :
                    length >= 1 ? new NativeDate(Y) :
                                  new NativeDate();
                // Prevent mixups with unfixed Date object
                date.constructor = Date;
                return date;
            }
            return NativeDate.apply(this, arguments);
        };

        // 15.9.1.15 Date Time String Format.
        var isoDateExpression = new RegExp("^" +
            "(\\d{4}|[\+\-]\\d{6})" + // four-digit year capture or sign + 6-digit extended year
            "(?:-(\\d{2})" + // optional month capture
            "(?:-(\\d{2})" + // optional day capture
            "(?:" + // capture hours:minutes:seconds.milliseconds
                "T(\\d{2})" + // hours capture
                ":(\\d{2})" + // minutes capture
                "(?:" + // optional :seconds.milliseconds
                    ":(\\d{2})" + // seconds capture
                    "(?:\\.(\\d{3}))?" + // milliseconds capture
                ")?" +
            "(?:" + // capture UTC offset component
                "Z|" + // UTC capture
                "(?:" + // offset specifier +/-hours:minutes
                    "([-+])" + // sign capture
                    "(\\d{2})" + // hours offset capture
                    ":(\\d{2})" + // minutes offset capture
                ")" +
            ")?)?)?)?" +
        "$");

        // Copy any custom methods a 3rd party library may have added
        for (var key in NativeDate) {
            Date[key] = NativeDate[key];
        }

        // Copy "native" methods explicitly; they may be non-enumerable
        Date.now = NativeDate.now;
        Date.UTC = NativeDate.UTC;
        Date.prototype = NativeDate.prototype;
        Date.prototype.constructor = Date;

        // Upgrade Date.parse to handle simplified ISO 8601 strings
        Date.parse = function parse(string) {
            var match = isoDateExpression.exec(string);
            if (match) {
                match.shift(); // kill match[0], the full match
                // parse months, days, hours, minutes, seconds, and milliseconds
                for (var i = 1; i < 7; i++) {
                    // provide default values if necessary
                    match[i] = +(match[i] || (i < 3 ? 1 : 0));
                    // match[1] is the month. Months are 0-11 in JavaScript
                    // `Date` objects, but 1-12 in ISO notation, so we
                    // decrement.
                    if (i == 1) {
                        match[i]--;
                    }
                }

                // parse the UTC offset component
                var minuteOffset = +match.pop(), hourOffset = +match.pop(), sign = match.pop();

                // compute the explicit time zone offset if specified
                var offset = 0;
                if (sign) {
                    // detect invalid offsets and return early
                    if (hourOffset > 23 || minuteOffset > 59) {
                        return NaN;
                    }

                    // express the provided time zone offset in minutes. The offset is
                    // negative for time zones west of UTC; positive otherwise.
                    offset = (hourOffset * 60 + minuteOffset) * 6e4 * (sign == "+" ? -1 : 1);
                }

                // Date.UTC for years between 0 and 99 converts year to 1900 + year
                // The Gregorian calendar has a 400-year cycle, so
                // to Date.UTC(year + 400, .... ) - 12622780800000 == Date.UTC(year, ...),
                // where 12622780800000 - number of milliseconds in Gregorian calendar 400 years
                var year = +match[0];
                if (0 <= year && year <= 99) {
                    match[0] = year + 400;
                    return NativeDate.UTC.apply(this, match) + offset - 12622780800000;
                }

                // compute a new UTC date value, accounting for the optional offset
                return NativeDate.UTC.apply(this, match) + offset;
            }
            return NativeDate.parse.apply(this, arguments);
        };

        return Date;
    })(Date);
}

//
// String
// ======
//

// ES5 15.5.4.20
// http://es5.github.com/#x15.5.4.20
var ws = "\x09\x0A\x0B\x0C\x0D\x20\xA0\u1680\u180E\u2000\u2001\u2002\u2003" +
    "\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u3000\u2028" +
    "\u2029\uFEFF";
if (!String.prototype.trim || ws.trim()) {
    // http://blog.stevenlevithan.com/archives/faster-trim-javascript
    // http://perfectionkills.com/whitespace-deviations/
    ws = "[" + ws + "]";
    var trimBeginRegexp = new RegExp("^" + ws + ws + "*"),
        trimEndRegexp = new RegExp(ws + ws + "*$");
    String.prototype.trim = function trim() {
        if (this === undefined || this === null) {
            throw new TypeError("can't convert "+this+" to object");
        }
        return String(this).replace(trimBeginRegexp, "").replace(trimEndRegexp, "");
    };
}

//
// Util
// ======
//

// ES5 9.4
// http://es5.github.com/#x9.4
// http://jsperf.com/to-integer
var toInteger = function (n) {
    n = +n;
    if (n !== n) { // isNaN
        n = 0;
    } else if (n !== 0 && n !== (1/0) && n !== -(1/0)) {
        n = (n > 0 || -1) * Math.floor(Math.abs(n));
    }
    return n;
};

var prepareString = "a"[0] != "a";
    // ES5 9.9
    // http://es5.github.com/#x9.9
var toObject = function (o) {
    if (o == null) { // this matches both null and undefined
        throw new TypeError("can't convert "+o+" to object");
    }
    // If the implementation doesn't support by-index access of
    // string characters (ex. IE < 9), split the string
    if (prepareString && typeof o == "string" && o) {
        return o.split("");
    }
    return Object(o);
};
});