MooTools implementation for Array.reduce() and Array.reduceRight()

Array.Reduce.js

/*
Script: Array.Reduce.js
	MooTools implementation for Array.reduce() and Array.reduceRight()

Acknowledgement:
	- Implementation code ported and reworked from Mozilla's Array.reduce() and Array.reduceRight() algorithms.
	  cf: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/reduce,
		  https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/reduceRight
*/

Array.implement({

	reduce: function(fn, initial, bind){
		var len = this.length, i = 0;
		if (len == 0 && arguments.length == 1) return null;
		var result = initial || this[i++];
		for (; i < len; i++) result = fn.call(bind, result, this[i], i, this);
		return result;
	},

	reduceRight: function(fn, initial, bind){
		var len = this.length, i = len - 1;
		if (len == 0 && arguments.length == 1) return null;
		var result = initial || this[i--];
		for (; i >= 0; i--) result = fn.call(bind, result, this[i], i, this);
		return result;
	}

});

Array.alias({reduce: 'foldl', reduceRight: 'foldr'});