How to access the property of the constructor?

Question

How can I access the color property of the constructor, from the setColor function?

function Obj() {
  this.color = undefined;
}

Obj.prototype.setColor = () => {
  for (var k = 0, hex = "0123456789ABCDEF", max = hex.length, random, color = ""; k < 6;
    ++k, random = Math.floor(Math.random() * max), color += hex[random]);
  this.color = "#" + color; // Here i need to change
};

var ball = new Obj();
ball.setColor();
console.log(ball.color);

So, I want to run the setColor function and change the color property of Obj the constructor.

What is the most elegant and simple method, without declare a var to the context and use that?

I'm sorry, I think I lacked information, now you can try my new snippet and see why I said, that "this.color" fails — carlos cerda diaz, Jan 02 '18 at 14:13
It fails because you are now using an arrow function. Don't use an arrow function. — Felix Kling, Jan 02 '18 at 14:13
@carloscerdadiaz Because arrow functions cannot be used as methods, lacking dynamic `this`. — Bergi, Jan 02 '18 at 14:22

score 1 · Accepted Answer · answered Jan 02 '18 at 14:10

1

The constructor doesn't have a color property.

The constructor function adds a color property to the instance as it is constructing it.

You can access the property on the instance with this.color (inside the function on the prototype).

function Obj() {
  this.color = "";
}

Obj.prototype.setColor = function() {
  for (var k = 0, hex = "0123456789ABCDEF", max = hex.length, random, color = ""; k < 6;
    ++k, random = Math.floor(Math.random() * max), color += hex[random]);
  this.color = "#" + color;
};

var instance = new Obj();
instance.setColor();
console.log(instance.color);

answered Jan 02 '18 at 14:10

Quentin

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I'm sorry, I think I lacked information, now you can try my new snippet and see why I said, that "this.color" fails – carlos cerda diaz Jan 02 '18 at 14:13
@carloscerdadiaz — Before you edited the code, you were using a function expression. Now you are using an arrow function, so `this` works differently. Don't use an arrow function. – Quentin Jan 02 '18 at 14:16
Why dont use arrow function ? you can explain me , please ? – carlos cerda diaz Jan 02 '18 at 14:16
@carloscerdadiaz — Because `this` works differently in arrow functions. – Quentin Jan 02 '18 at 14:17

How to access the property of the constructor?

1 Answers1