Object variable initialization

Question

I have such a simple code

var q = {
  p1: 'kv3',
  p2: 'http://google.com/' + this.p1
};

console.log(q.p2);

which I expect to output the p2 + p1, but for some reason the p1 seems to be undefined when I console.log. Isn't p1 initialized before p2?

What would be the correct code for this?

tadman · Accepted Answer · 2016-02-25 23:03:13Z

3

Remember that this is does not suddenly refer to q inside of the object declaration:

var p1 = 'kv3';

var q = {
  p1: p1,
  p2: 'http://google.com/' + p1
};

answered Feb 25, 2016 at 23:03

tadman

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Comments

millerbr · Accepted Answer · 2016-02-25 23:02:52Z

2

The object q is initialised all in one, so everything inside it is inaccessible until the whole thing is done initialising. Try this:

var q = {
    p1: 'kv3'
};
q.p2 = 'http://google.com/' + q.p1

console.log(q.p2);

answered Feb 25, 2016 at 23:02

millerbr

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Oriol · Accepted Answer · 2016-02-25 23:04:59Z

2

this is an additional parameter that functions (except arrow ones) receive when they are called.

Therefore, that this does not refer to the object (it has not been created yet anyways).

But you can instantiate an anonymous function instead:

var q = new function() {
  this.p1 = 'kv3';
  this.p2 = 'http://google.com/' + this.p1;
};

answered Feb 25, 2016 at 23:04

Oriol

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