this properties with different values, inside constructor

Question

I know this is empty in the beginning of a contructor function, and gets filled until it's automatically returned.

function Elf(_name, _weapon) {
 
  //empty this
 console.log('this a', this); // {}

 this.name = _name;
 this.weapon = _weapon;
 
 // this with props
 console.log('this b', this); // {name: "Sam", weapon: "bow"}
}

let sam = new Elf("Sam", "bow");

In the node console and this snippet, the result is what i expected:

this a {}
this b { "name": "Sam", "weapon": "bow" }

But in the Chrome's console, i get:

   this a Elf {}
name: "Sam"
weapon: "bow"
__proto__: Object

this b Elf {name: "Sam", weapon: "bow"}
name: "Sam"
weapon: "bow"
__proto__: Object

why are those name and weapon properties already filled? If you'r gonna mention hoisting, and that the reference to this becomes global, why the difference between the two logs?

It's an issue with the way chrome logs things [see also](https://stackoverflow.com/questions/11284663/console-log-shows-the-changed-value-of-a-variable-before-the-value-actually-ch) | [and this](https://stackoverflow.com/questions/23392111/console-log-async-or-sync) — Mark, Jun 30 '19 at 17:45
Possible duplicate of [Wrong value in console.log](https://stackoverflow.com/questions/11214430/wrong-value-in-console-log) and [Is Chrome's JavaScript console lazy about evaluating arrays?](https://stackoverflow.com/questions/4057440) — adiga, Jun 30 '19 at 17:46

score -2 · Answer 1 · answered Jun 30 '19 at 17:44

Try in chrome console the following code

function Elf(_name, _weapon) {
    console.log('before', this.name);

    this.name = _name;
    this.weapon = _weapon;

    console.log('after', this.name);
}

let sam = new Elf("Sam", "bow");

You will get expected result. Maybe logging in chrone console is not 'immediate' and thus, this is filled with value before displaying.

this properties with different values, inside constructor

1 Answers1