This function returns a deep copy of a list or object.

copyItem.js

copyItem = function(item, shallow) {
	var itemProto = Object.prototype.toString.call(item);
	var newItem = item;
	var getItem = function(child) { return !shallow ? copyItem(child) : child; };
	if (itemProto === Object.prototype.toString.call([])) {
		newItem = [];
		for (var itemIndex=0, len=item.length; itemIndex < len; itemIndex++) newItem.push(getItem(item[itemIndex]));
	}
	if (itemProto === Object.prototype.toString.call({})) {
		newItem = {};
		for (var itemIndex in item) newItem[itemIndex] = getItem(item[itemIndex])
	}
	return newItem;
}

I changed the for-loop for arrays, as according to this StackOverflow answer arrays shouldn't be iterated using the for-in statment.

http://stackoverflow.com/questions/3010840/loop-through-array-in-javascript