How to assign a variable to another variable inside an object in javascript

Question

myObj={
a: 10,
b: this.a
}
console.log('b :',myObj.b)

this gives value of b as undefined. What is the correct way to do this.

Why don't you assign the shared value to a variable outside the object, and assign that to both of them? — Dominic, Feb 21 '18 at 11:28
You cannot do that, **this** does not exists before the } ends. — Munim Munna, Feb 21 '18 at 11:29
Post your full code, Surely there are other ways to do what you are trying. — Munim Munna, Feb 21 '18 at 11:53

Ankit Agarwal · Answer 1 · 2018-02-21T11:32:22.317

3

You can use the simple way to get that value in a new property of that same object as JavaScript does not work like the way you are expecting,

var myObj={
   a: 10
};
myObj.b = myObj.a;
console.log('b :',myObj.b)

edited Feb 21 '18 at 11:32

answered Feb 21 '18 at 11:29

Ankit Agarwal

30,378
5
37
62

the question clearly says inside an object, this is not the answer – Munim Munna Feb 21 '18 at 11:30

score 0 · Answer 2 · answered Feb 21 '18 at 11:31

Your this is currently the global object, which is undefined. You can either create a function (closure) to ensure your this is what you want. Or you can either create a globar var outside that object and assign a property of that object to it.

I'm not sure what you're trying to accomplish though.

If you want an example, you can do for example:

function Person() {
   this.a = 10;
   this.b = this.a; // is this what you want? (why?)
}

Then, you can create a Person typing var x = new Person().

Anyway, what happened here was, I created a javascript closure (aka function) which has its this attribute. Or else this will be undefined (Unless you're on a browser, in that case it will be window, or, if you're on node, it will be the global object).

score 0 · Answer 3 · answered Feb 21 '18 at 11:31

0

Add a constructor or another function that sets this.b = this.a

answered Feb 21 '18 at 11:31

Leon Marzahn

341
4
15

Vinod Ghunake · Answer 4 · 2018-04-13T07:12:39.887

-1

try such that

myObj={
a: 10,
b: a
}



var myObj={ 
a: 10,
b:this.c,
c:function() {
this.b=this.a;
     return this.b;
}

look here http://jsfiddle.net/36vfy4yu/

edited Apr 13 '18 at 07:12

answered Feb 21 '18 at 11:31

Vinod Ghunake

306
2
7

You tried that yourself before posting? – Munim Munna Feb 21 '18 at 11:32
correct this answer, I'll remove the downvote. – Munim Munna Mar 05 '18 at 14:37

score -1 · Answer 5 · answered Feb 21 '18 at 11:44

-1

If you really want to assign a property with a reference to another property INSIDE the same object you are just creating, you can create an object from an anonymous function constructor, like so:

var object = new (function() {
   this.a = 3;
   this.b = this.a;
})()

And then you can reference like so:

console.log(object.a) // 3
console.log(object.b) // 3

answered Feb 21 '18 at 11:44

filipbarak

1,835
2
17
28

[Never ever use `new function`!](https://stackoverflow.com/q/10406552/1048572) – Bergi Feb 21 '18 at 11:49
Okay, try to instantiate the function without the new keyword and see if you can log `object.a` or `object.b`. And anyway, the question is specifically how to assign a property referencing another property of the same object that's being declared. – filipbarak Feb 21 '18 at 11:52
function SetValues() { var b=null; var myObj={ a: 10, b:this.c, c:function() { this.b=this.a; //alert("a:"+myObj.a); alert("in function b:"+myObj.b); return this.b; } } alert("Out Side b:"+myObj.c()); } – Vinod Ghunake Apr 13 '18 at 07:07

How to assign a variable to another variable inside an object in javascript

5 Answers5