CODEWITHSUNDEEP
javascriptobject
slinkhi
slinkhi

Reputation: 989

javascript "execute-all" method for all instances of an object

Let's say I have the following:

function FooBar (s) {
  this.s = s;
  this.logS = function () { console.log(this.s)}
}
var Foo = new FooBar('foo');
var Bar = new FooBar('bar');

My goal is to call .logS() for every instance of FooBar. I can do this by calling them individually:

Foo.logS();
Bar.logS();

But let's say I do not know the names of all the objects of type FooBar - is there a method to execute all of them? For example, in principle I want to have this line of code: FooBar.logS() equate to calling Foo.logS() and Bar.logS().

Well that obviously doesn't work, but I'm looking for something like that in principle. Failing that, is there a way to get a list of names of all objects that are instanceof FooBar?

For example, I can do this:

for (var o in window) { 
  if (window[o] instanceof FooBar) {
    window[o].logS();
  }
}

But that only works for objects directly under window. If I were to say do this...

var bazs = [new FooBar('baz')];

...the loop wouldn't work. I suppose I could make a function to recursively walk through window but I think at best that would be slow but may not even find all of them (maybe?)

TL;DR

The goal is to find every object where (object instanceof FooBar) regardless of where object nested within window

Possible?

Edit: Clarification

I apologize, it seems I was not being clear enough. The suggested methods for keeping track of instances as they are created are great (array, subscription), but it's not what I need.

More detailed scenario. There is a 3rd party script that is used multiple times throughout a webpage. I get to insert my own code at the bottom of the page. So, I do not get to alter FooBar to keep track of things from the get-go, before any instances of it are created. So my code needs to find all instances of FooBar that already exist when my code is executed.

Upvotes: 2

Views: 1509

Answers (1)

Felix Kling
Felix Kling

Reputation: 816462

You could make so that creating a new instance of FooBar adds that instance to an array. E.g.:

function FooBar() {
    FooBar.instances.push(this);
    // ...
}
FooBar.instances = [];

FooBar.logS = function() {
    FooBat.instances.forEach(function(instance) {
        instance.logS();
    });
};

Alternatively you could implement an event handling or publish/subscriber system where each instance of FooBar listens to a specific event, which you then simply trigger. E.g.

function FooBar() {
    // ...
    Arbiter.subscribe('logS', this.logS.bind(this));
}

Arbiter.inform('logS');

If you don't want to implement something like this on your own, there are existing libraries out there, e.g. https://github.com/mroderick/PubSubJS

Upvotes: 2

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