Array.prototype.map = function(callback, thisArg) {

	var T, A, k;

	if (this == null) {
		throw new TypeError(' this is null or not defined');
	}

	// 1. Let O be the result of calling ToObject passing the |this|
	//    value as the argument.
	var O = Object(this);

	// 2. Let lenValue be the result of calling the Get internal
	//    method of O with the argument "length".
	// 3. Let len be ToUint32(lenValue).
	var len = O.length >>> 0;

	// 4. If IsCallable(callback) is false, throw a TypeError exception.
	// See: http://es5.github.com/#x9.11
	if (typeof callback !== 'function') {
		throw new TypeError(callback + ' is not a function');
	}

	// 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
	if (arguments.length > 1) {
		T = thisArg;
	}

	// 6. Let A be a new array created as if by the expression new Array(len)
	//    where Array is the standard built-in constructor with that name and
	//    len is the value of len.
	A = new Array(len);

	// 7. Let k be 0
	k = 0;

	// 8. Repeat, while k < len
	while (k < len) {

		var kValue, mappedValue;

		// a. Let Pk be ToString(k).
		//   This is implicit for LHS operands of the in operator
		// b. Let kPresent be the result of calling the HasProperty internal
		//    method of O with argument Pk.
		//   This step can be combined with c
		// c. If kPresent is true, then
		if (k in O) {

			// i. Let kValue be the result of calling the Get internal
			//    method of O with argument Pk.
			kValue = O[k];

			// ii. Let mappedValue be the result of calling the Call internal
			//     method of callback with T as the this value and argument
			//     list containing kValue, k, and O.
			mappedValue = callback.call(T, kValue, k, O);

			// iii. Call the DefineOwnProperty internal method of A with arguments
			// Pk, Property Descriptor
			// { Value: mappedValue,
			//   Writable: true,
			//   Enumerable: true,
			//   Configurable: true },
			// and false.

			// In browsers that support Object.defineProperty, use the following:
			// Object.defineProperty(A, k, {
			//   value: mappedValue,
			//   writable: true,
			//   enumerable: true,
			//   configurable: true
			// });

			// For best browser support, use the following:
			A[k] = mappedValue;
		}
		// d. Increase k by 1.
		k++;
	}

	// 9. return A
	return A;
};