I have a couple of nested objects, where A is always a part of B.
May I use the following code to access owner's properties and methods?
function A( owner ) {
this.value = function () { return owner.value() + 1 };
}
function B() {
this.value = function () { return 1; };
this.a = new A( this );
}
var b = new B();
alert( b.a.value() );
Actually, it works. But I would like to know whether it is correct or not.
You may consider to move the methods declaration from the constructors to the prototypes of the constructors. You will save memory if you have a lot of objects A and B, because in your sample for every object there will be a copy of the method inside of it. Moving a method declaration to the prototype will allow all objects to share a single copy of this method. But you will have to keep a reference to the "owner" in A (now you use closures to keep a reference to it).
Actually, it works. But I would like to know whether it is correct or not.
It works because you create new instance of parent and access it there:
this.a = new A( this );
The correct way (for inheritence) is to set child's prototype and constructor:
A.prototype = new B();
A.prototype.constructor = A;
For more explanation, have a look at this question.
this.fooreferences a field of a new object whose prototype isA.prototypeif your call site invokesnew A()(as opposed to justA()orA.call(someObject), in which casethisdepends on the way the function is called). \$\endgroup\$