Simple routines for ordering database data in javascript

collectionOrder.js

var collectionOrder = function(options) {
	this.itemCount = options.itemCount;
	this.move = options.move;
	this.fetch = options.fetch;
	if (typeof options.batchMove !== "undefined") {
		this.batchMove = options.batchMove;
	} else {
		this.batchMove = this._batchMoveInternal;
	}
};
collectionOrder.prototype.moveItemToIndex = function(fromIndex, toIndex) {
	var item = this.fetch(fromIndex);

	if (toIndex > fromIndex) {
		this.batchMove(fromIndex + 1, toIndex - fromIndex, -1);
	} else {
		this.batchMove(toIndex, fromIndex - toIndex, 1);
	}
	this.move(item, toIndex);
};
collectionOrder.prototype._batchMoveInternal = function(fromIndex, length, movement) {
	if (movement == -1) {
		for (i = 0; i < length; i++) {
			var iItem = this.fetch(i + fromIndex);
			this.move(iItem, i + fromIndex + movement);
		}
	} else {
		for (i = length - 1; i >= 0; i--) {
			var iItem = this.fetch(i + fromIndex);
			this.move(iItem, i + fromIndex + movement);
		}
	}
}

// example code

var items = [
	'ali', 'veli', 'deli', 'kirk', 'dokuz', 'elli'
];

var order = new collectionOrder({
	itemCount: items.length,
	move: function(item, toIndex) {
		console.log("\tMoving Item '" + item + "' to " + toIndex);
		var hold = null;
		if (items[toIndex]) {
			hold = items[toIndex];
		}
		items[toIndex] = item;
		return hold;
	},
	fetch: function(itemIndex) {
		console.log("Fetching Item [" + itemIndex + "] : '" + items[itemIndex] + "'");
		return items[itemIndex];
	}
});

order.moveItemToIndex(0, 5);
console.log(items);

// mongoose example (not tested)

var query = { category_id: 5 }; // ex: ordering items in a category

MyObjectModel.find(query, '_id order', { sort: { order: 1 } }, function (err, docs) {
	
	var order = new collectionOrder({
		itemCount: docs.length,
		move: function(item, toIndex) {
			item.order = toIndex;
			item.save();
		},
		fetch: function(index) {
			return _.findWhere(docs, { // underscore.js
				"order": index
			});
		},
		batchMove: function(fromIndex, length, movement) { // this is optional. to reduce queries.
			var updateQuery = query;
			updateQuery.order = { $gte: fromIndex, $lt: fromIndex + length };
			MyObjectModel.update(updateQuery, { $inc: { order: movement } } );
		}
	});
	order.moveItemToIndex(3, 15); // pops theItem at index 3, shifts 4..15 to left, and puts theItem into index:15.
	
});