Is this a safe way to reference objects in JavaScript?

Question

If I were to define two objects myDataStore and myDrawer something like this:

var myDataStore = function(myObjectRef) {
    this.myInternalObject = myObjectRef;
};

var myDrawer = function(myObjRef) {
    this.myInternalObject = myObjectRef;
};

And if I were to create an object like so:

[[EDIT - Adjusted Object Creation to Ensure 'this' is being mapped to myObject, not the global window object]]

(function(){
  var myObject = window.myObject = function(){
      this.dataStore = new myDataStore(this);
      this.drawer = new myDrawer(this);
  }
 })();

Then myObject.dataStore.myInternalObject, and myObject.drawer.myInternalObject, would simply be pointers back to the original 'myObject' - not taking up any additional memory in the browser. Yes?

I am interested in implementing techniques like this - as it makes it easy for objects to communicate with each other.

Answer 1

No. myObject.dataStore.myInternalObject and myObject.drawer.myInternalObject will both point to the global object (mapped to window in browsers), unless you're inside a function already when you declare myObject. In other words, it will be set to whatever this is in the context in which you declare myObject. It won't be myObject itself.

Answer 2

Nope. this refers to whatever is on the left hand side of the . or if there is no left hand side of the . then it's the global object.

So if you did this:

var MyObj = {
   "create": function() {
      var myObject = {
         dataStore = new myDataStore(this);
         drawer = new myDrawer(this);
      }; 
   }
}; 
MyObj.create();

this would be MyObj. If you did this:

var myObject = {
   dataStore = new myDataStore(this);
   drawer = new myDrawer(this);
}; 

(not in a function) this would be window (assuming this is in a browser).

Answer 3

Yes, your assumption is correct. myInternalObject will be a reference and not a new object. You can test it like this:

var MyDataStore = function(myObjectRef) {
    this.myInternalObject = myObjectRef;
};

var data = {
    value: "value"
};
var dataStore = new MyDataStore(data);
data.value = "test";
console.log(dataStore.myInternalObject);  // logs { value : "test" } instead of { value: "value" }