8

If I have an object like this:

obj = {a:{aa:1}, b:2};

and I want to create a shortcut variable (pointer to obj.a.aa) x like this:

x = obj.a.aa;

and then I want to assign the value 3 to obj.a.aa using x like this:

x = 3;  // I would like for obj.a.aa to now equal 3
console.log(obj.a.aa); // 1  (I want 3)

How can I set x up to result in the value 3 going into obj.a.aa?

I understand that obj.a.aa is a primitive, but how can I define a variable that points to it which I can then use to assign a value to the property?

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3 Answers 3

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9

You cannot use x = value as that will not keep any references, just a copy. You would have to reference the parent branch in order to do so:

x = obj.a;

then set the value:

x.aa = 3;
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2 Comments

So I have to stay one level higher than the property value by always referencing the direct parent object?
@ChrisG. For value types yes.
3

Or, use a function:

var set_x = function(val){
  obj.a.aa = val;
}
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0

Of course you can't - you're not trying to modify the reference that is the name of the object property, you're trying to modify the object. To modify the object, you'll need a reference to the object.

That being said there's probably a creative way to do this. Create a function that takes as a constructor the object, and give the function a customer = setter or method that modifies the object reference. Something like this might work.

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