Recursive function jquery with backbone

Question

I have an app in backbone where I want to find inside a Json some records and print out.

my JSON is like this:

[
  {
    \"id\" : \"r1\",
    \"hotel_id\         


        

Answer 1

Based on @Bergi's answer, I came up with this. It should solve your problem.

Here is a demo: http://plnkr.co/edit/NHE9V5?p=preview

Updated I have modified some things to accomodate your separate JSON files.

Cartesian Product Helper (http://en.wikipedia.org/wiki/Cartesian_product)

function cartesian(arg) {
  arg = arg || [];
  var r = [],
        max = arg.length - 1;

    function helper(arr, i) {
        for (var j = 0, l = arg[i].length; j < l; j++) {
            var a = arr.slice(0); // clone arr
            a.push(arg[i][j]);
            if (i == max) {
                r.push(a);
            } else helper(a, i + 1);
        }
    }
  if(arg.length > 0)
      helper([], 0);
    return r;
}

Nested Collection Solution

HotelModel = Backbone.Model.extend({
    initialize: function() {
        // because initialize is called after parse
        _.defaults(this, {
            rooms: new RoomCollection()
        });
    },
    parse: function(response) {
        if (_.has(response, "rooms")) {
            this.rooms = new RoomCollection(response.rooms, {
                parse: true
            });
            delete response.rooms;
        }
        return response;
    },
    toJSON: function() {
        var json = _.clone(this.attributes);
        json.rooms = this.rooms.toJSON();
        return json;
    },
    addRoom: function(rooms, options) {
        return this.rooms.add(rooms, options);
    },
    removeRoom: function(rooms, options) {
        return this.rooms.remove(rooms, options);
    },
    createRoom: function(attributes, options) {
        return this.rooms.create(attributes, options);
    },
    getCombinations: function() {
        return cartesian(_.values(this.rooms.groupBy('level')));
    }
});

RoomModel = Backbone.Model.extend({});

HotelCollection = Backbone.Collection.extend({
    model: HotelModel,
  getAllCombinations: function(){
    return this.map(function(hotel){
      return _.extend(hotel.toJSON(), {
        combinations: hotel.getCombinations()
      });
    });
  }
});

RoomCollection = Backbone.Collection.extend({
    model: RoomModel,
    getRoomsByHotelId: function(hotelId) {
        return this.where({
            hotelId: hotelId
        });
    }
});

Loading of the Separate JSON

var hotels = new HotelCollection([], {
    url: 'hotels.json'
});
var rooms = new RoomCollection([], {
    url: 'rooms.json'
});

hotels.fetch({
    success: function() {
        rooms.fetch({
            success: function() {
                hotels.each(function(hotel) {
                    hotel.addRoom(rooms.getRoomsByHotelId(hotel.id));
                });
                // all done here
                var combos = hotels.getAllCombinations();
                $(function() {
                    $('body').append('<pre>' + JSON.stringify(combos, null, 2) + '</pre>');
                });
            }
        });
    }
});

hotels.json

[{
  "id": 1,
    "name": "Hotel One"
}, {
    "id": 2,
    "name": "Hotel Two"
}, {
    "id": 3,
    "name": "Hotel Three"
}]

rooms.json

[{
  "level": 1,
    "name": "Room A",
    "hotelId": 1
}, {
    "level": 1,
    "name": "Room B",
    "hotelId": 1
}, {
    "level": 2,
    "name": "Room A",
    "hotelId": 1
}, {
    "level": 2,
    "name": "Room B",
    "hotelId": 1
}, {
    "level": 1,
    "name": "Room A",
    "hotelId": 2
}, {
    "level": 1,
    "name": "Room B",
    "hotelId": 2
}, {
    "level": 2,
    "name": "Room A",
    "hotelId": 2
}, {
  "level": 2,
    "name": "Room B",
    "hotelId": 2
}, {
  "level": 1,
  "name": "Room A",
    "hotelId": 3
}, {
  "level": 1,
  "name": "Room B",
  "hotelId": 3
}, {
  "level": 1,
  "name": "Room C",
  "hotelId": 3
}]

Answer 2

First you should split your rooms list by hotels and levels:

var rooms = _(allRooms.groupBy, "hotel_id");
for (var hotelid in rooms)
    rooms[hotelid] = _.groupBy(rooms[hotelid], "level");

The "combinations" you're looking for is the cartesian product of the levels (for each hotel). You can use this helper function for example. Use it like this:

_.each(this.collection.models, function(hotel) {
    var levels = rooms[hotel.id];
    var combinations = cartesian(_.values(levels));
    // put them on the hotel
});