Javascript Access to parent properties from child method

Question

I have a Campaign object with a campaign_offer array property which contains N CampaignOffer children.

My goal is to access to the Campaign object inside each CampaignOffer object.

To achieve this, I've added in the CampaignOffer object a parent property which contains the Campaign object.

// Parent
var Campaign = function (properties) {
    this.id = properties.id || null;
    this.campaign_offer = [];
};

// Parent: Add a new child in array of children
Campaign.prototype.addOffer = function (offer) {
    // Pass the parent reference to the child
    offer.parent = this;

    this.campaign_offer.push(offer);
};

// Child
var CampaignOffer = function (properties) {
    this.name = properties.name || null;
    this.parent = properties.parent || null;
};

// ---------------------------------------------

// Create the parent
var campaign = new Campaign({ id: 1 });

// Create the child
var campaign_offer = new CampaignOffer({ name: 'test' });

console.log('Offer without parent', campaign_offer);

// Add the child to the parent
campaign.addOffer(campaign_offer);

console.log('Offer with parent', campaign_offer);

You can see the result there: Fiddle

The problem is that when you browse the second console.log(). You can find too much recursiveness. Like:

parent.campaign_offer[0].parent.campaign_offer[0].parent.campaign_offer[0]...

I understand this output but don't know how to avoid this. What about defining a max depths?

Btw it doesn't make an infinite loop.

Your objects have a reference to each other - every time you expand the properties, you see the same references. It's not a problem - you just have to understand that it will happen while you're inspecting stuff. — James Thorpe
– James Thorpe, Commented Oct 15, 2015 at 13:01
Why does the relationshp have to be two-way? I can see why CampaignOffer might need to reference a Campaign object, but I can't see any reason for the converse. (I'd also call it campaign rather than parent, but that's a style thing.) You can do that, and it's harmless unless you write code that tries to traverse it and doesn't understand that it may circle back, but I don't see any need for it. — T.J. Crowder
– T.J. Crowder, Commented Oct 15, 2015 at 13:01

T.J. Crowder · Accepted Answer · 2015-10-15 13:10:58Z

2

I understand this output but don't know how to avoid this. What about defining a max depths?

You don't have multiple depths here, to speak of, you just have a circular reference:

  /---------------------------------------------------------------------\
  |  +----------------+                                                 |
  +->|    campaign    |                                                 |
     +----------------+                                                 |
     | id: xxx        |         +----------+                            |
     | campaign_offer |-------->| (array)  |                            |
     +----------------+         |----------+        +----------------+  |
                                | 0        |------->| campaign_offer |  |
                                +----------+        +----------------+  |
                                                    | name: xxx      |  |
                                                    | parent         |--/
                                                    +----------------+

Circular references are fine provided you don't write code traversing them that is unaware that they may exist, as that code may end up looping forever.

I don't see any need for one in this case, it seems like CampaignOffer having a Campaign makes sense, but I don't see much point to the converse (the campaign_offer array). But again, it's fine, just don't write code that tries to follow these to their end, as they don't have an end.

answered Oct 15, 2015 at 13:10

T.J. Crowder

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2 Comments

T.J. Crowder Over a year ago

@JamesThorpe: :-) Love me some ASCII-art.

Syl Over a year ago

Thanks dude & all replyers! :)

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