Backbone Get or Fetch method

backbone.getOrFetch.js

Backbone.Collection.prototype.getOrCreate = function(id){

	var model = this.get.apply(this, arguments)

	// if no model, fetch and add the requested model
	if( !model ){

		id = id instanceof Backbone.Model ? id.id : id;
		var ModelClass = this.model || Backbone.Model;

		var data = {}
		data[ModelClass.prototype.idAttribute] = id;

		// support for Backbone Relational
		var model = ModelClass.findOrCreate
				? ModelClass.findOrCreate(data)
				: new ModelClass(data);

		model.needsFetching = true;

		// add model to this collection
		this.add(model);
	}

	return model;
}

Backbone.Collection.prototype.getOrFetch = function(id, success){

	var model = this.getOrCreate.apply(this, arguments)

	// only one means we just created this model
	if( model.needsFetching ){

		delete model.needsFetching;
		model.isFetching = true;

		model.fetch({success: function(){
			delete model.isFetching
			if( success ) success(model)
		}});
	}else{
		if( success ) success(model)
	}

	return model;
}