I apologize that I don't know of a better way of titling my question--suggestions appreciated. I know that this is valid:
var cyclic = new Object();
cyclic.c = cyclic;
and that this doesn't break
var cyclic = {c: this};
So I was wondering--why doesn't this work?
var foo = {a: 10, b: 5, c:(this.a - this.b)};
Is it because the elements reference other elements at the same 'level', or that I'm trying to do it all in one step? Is there a way to do this sort of thing in one line?
this isn't the literal object it's the window object because you're not calling it with a function.
You could/should utilise a constructor function for this instead,
consider the function below
var Foo = function(a, b) {
this.a = a; //if you want to save state inside the object
this.b = b; //else skip it.
this.c = a - b;
}
//create a new object from Foo
var foo = new Foo(10, 5);
foo.c
>> 5
this doesn't point to what you think it does. When inside a function, this will point to the object that function was called on:
var o = { foo : function(){ console.log(this); } };
o.foo() // will log o
var o2 = { {bar : {foo : function(){ console.log(this); } } };
o2.bar.foo() // will log o2.bar
If the function is not called on any object or if this is not inside a function, then it will point to the global object, window.
var foo = function() { console.log(this); };
foo(); // will log window
console.log(this) // will log window
When you do:
var cyclic = {c: this};
You have created an object named cyclic which has a property c which references the global object.
Similarly, when you do:
var foo = {a: 10, b: 5, c:(this.a - this.b)};
You create an object with a property which references the a and b properties of the global object.
One thing you could do is create an init function:
var foo = { a:10, b:5, init : function(){ this.c = this.a - this.b } };
To have this be foo, you simply need to call the function as foo.init().
foo.init(); // adds the c property to foo, with the value foo.a-foo.b
console.log(foo.c);
