Javascript Object Literal referring to another property in itself from another property

Question

I have a object literal:

var obj = {
    a : document.getElementById("ex1"),
    b : obj.a.document.getElementsByTagName("div")
};

I am having trouble with the b property, for some reason it is not letting that happen. Is this possible?

possible duplicate of Self-references in object literal declarations — zzzzBov
– zzzzBov, Commented Jun 18, 2013 at 20:29

user993683 · Accepted Answer · 2018-09-16 14:51:16Z

6

The modern way to do this is with getter methods:

let obj = {
  firstName: "A’dab",
  lastName: "Farooqi"
  get fullName() {
    return this.firstName+" "+this.lastName;
  },
}

So now you can just write obj.fullName - no need for the parentheses on the end.

answered Sep 16, 2018 at 14:51

user993683

Sign up to request clarification or add additional context in comments.

2 Comments

Almir Campos Over a year ago

This should be accepted as the corrected answer, given the most recent updates of the JavaScript. Also, this his a powerful feature that should be more disseminated among developers.

bsplosion Over a year ago

Seconded - I wish I'd learned about this a long time ago. This is incredibly useful for establishing complex configurations with generic callables for some properties.

Tomasz Nurkiewicz · Accepted Answer · 2012-02-16 19:27:40Z

2

You need two steps:

var obj = {
    a : document.getElementById("ex1")
};

obj.b = obj.a.document.getElementsByTagName("div")

Or:

var temp = document.getElementById("ex1")
var obj = {
    a : temp,
    b : temp.document.getElementsByTagName("div")
};

answered Feb 16, 2012 at 19:27

Tomasz Nurkiewicz

342k72 gold badges713 silver badges680 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 11:48:00Z

2

When the property b is being defined, obj is not defined yet. One way to get around that problem is to make your property a function so that it's not evaluated until called.

var obj = {
    a : document.getElementById("ex1"),
    b : function() {
      // This is not evaluated until obj.b() is called
      return obj.a.document.getElementsByTagName("div");
    }
};
obj.b();

If you really want it to be a property, you have to do it in two steps as Tomasz Nurkiewicz shows

edited May 23, 2017 at 11:48

CommunityBot

11 silver badge

answered Feb 16, 2012 at 19:28

Ruan Mendes

92.7k31 gold badges161 silver badges225 bronze badges

3 Comments

user123444555621 Over a year ago

You could use a getter method in browsers that support it var obj={a:document.getElementById("ex1"),get b(){return this.a.document.getElementsByTagName("div")}};

Ruan Mendes Over a year ago

@Pumbaa80 By browsers that support it, you mean Firefox only??? A better approach would be to use Object.defineProperty since it's available in the latest version of all browsers, but that also requires multiple steps

user123444555621 Over a year ago

Actually, all browsers but IE<=8 support it. Browser support for defineProperty is the same.

Collectives™ on Stack Overflow

Javascript Object Literal referring to another property in itself from another property

3 Answers 3

2 Comments

Comments

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related