Array.prototype.reduce = function(callback /*, initialValue*/) {
	'use strict';
	if (this === null) {
		throw new TypeError('Array.prototype.reduce called on null or undefined');
	}
	if (typeof callback !== 'function') {
		throw new TypeError(callback + ' is not a function');
	}
	var t = Object(this), len = t.length >>> 0, k = 0, value;
	if (arguments.length == 2) {
		value = arguments[1];
	} else {
		while (k < len && !(k in t)) {
			k++;
		}
		if (k >= len) {
			throw new TypeError('Reduce of empty array with no initial value');
		}
		value = t[k++];
	}
	for (; k < len; k++) {
		if (k in t) {
			value = callback(value, t[k], k, t);
		}
	}
	return value;
};