If I decide to add forEach to Marrow

foreach.js

Marrow.prototype.forEach = function(obj, fn){

	if("forEach" in obj){
		obj.forEach(fn); // native knows best
	}else if("length" in obj){ // array
		for(var i = 0; i < obj.length; i += 1){
			fn(obj[i], i);
		}
	}else if(typeof obj === "object"){ // object
		for(var key in obj){
			fn(obj[key], key);
		}
	}else{
		fn(null); // nothing
	}

};