Question

I’ve got a mentally taxing problem here, where I’ve got a JSON object retrieved using a collection in Backbone. This is what the object looks like:

{
    "MatchID": "00000001",
    "Date": "1970-01-01T00:00:00.000Z",
    "OriginalID": "",
    "Stage": {
        "StageNumber": "0",
        "StageType": "Stage Type"
    },
    "Round": {
        "RoundNumber": "0",
        "Name": "Round Name"
    },
    "Leg": "1",
    "HomeTeam": {
        "TeamID": "0",
        "Name": "Home Team Name"
    },
    "AwayTeam": {
        "TeamID": "0",
        "Name": "Away Team Name"
    },
    "Venue": {
        "VenueID": "0",
        "Name": "Venu Name"
    },
    "Referee": null,
}

What I want to do with this data, is filter it based on a particular attribute, such as the Venue.Name or Date attributes (which are different depths into the object, and can be deeper than two levels for some of the other data). I’ve got the following code inside a Backbone collection to filter and return a new collection with the contents filtered appropriately:

findWhere: function (Attribute, Value)
{
    return new Project.Collections.Fixtures(this.filter(function (fixture)
    {
        return eval('fixture.attributes.' + Attribute) == Value;
    }));
}

This allows me to specify in an attribute which attribute I want to filter by, and what I want it to be equal to, for any depth of object. The problem is, I really don’t want to use “eval” to do this, but obviously I can’t use “[Attribute]” for something like “AwayTeam.TeamID”, as it won’t work.

Does anyone know of a method I can use to achieve this functionality without using eval?

Answer 1

Something like this would let you traverse the hierarchy of objects to find a value:

var x = {
    y: {
        z: 1
    }
};

function findprop(obj, path) {
    var args = path.split('.'), i, l;

    for (i=0, l=args.length; i<l; i++) {
        if (!obj.hasOwnProperty(args[i]))
            return;
        obj = obj[args[i]];
    }

    return obj;
}

findprop(x, 'y.z');

You could add this as a method to your Fixtureobject:

Fixture = Backbone.Model.extend({
    findprop: function(path) {
        var obj = this.attributes,
            args = path.split('.'), 
            i, l;

        for (i=0, l=args.length; i<l; i++) {
            if (!obj.hasOwnProperty(args[i]))
                return;
            obj = obj[ args[i] ];
        }
        return obj;
    }
});

and use it to extract the value

var f = new Fixture();
f.findprop("HomeTeam.TeamID");

The findWhere method could then be rewritten as

findWhere: function (Attribute, Value)
{
    return new Project.Collections.Fixtures(this.filter(function (fixture){
        return fixture.findprop(Attribute) === Value;
    }));
}

And a Fiddle to play with http://jsfiddle.net/nikoshr/wjWVJ/3/