WeakMaps() JS OOP tutorial

JavaScript
1

I am using the exact code he uses in ES6 Classes( Private Members Using WeakMaps.) From the beginning to 2:34 in the video. The draw method is in the prototype, but I can not get the radius value. When I type c.draw() in the console it says undefined

2

Can you include your code? Here’s how to format it for a post.

3

`const _radius = new WeakMap();

class Circle {
constructor(radius) {
_radius.set(this, radius);
}

draw() {
console.log(_radius.get(this));
}
}

const c = new Circle(1);

4

The console is showing you the return value of the draw method, but your draw method has no return value. In other words, the return value is undefined. If you return a value, then you will see that value in the console.

draw() {
  const value = _radius.get(this);
  return value;
}
5

I tried your code and I get the same result. I think the behavior of WeakMaps has changed since this video. I didn’t have any issues with the preceding Symbols exercise.
`const _radius = new WeakMap();

class Circle {
constructor(radius) {
_radius.set(this, radius);
}

draw() {
const value = _radius.get(this);
return value;
}
}
const c = new Circle(1);

6

If you run this code you don’t see The radius is: 1?

const _radius = new WeakMap();

class Circle {
  constructor(radius) {
    _radius.set(this, radius);
  }

  draw() {
    const value = _radius.get(this);
    return value;
  }
}

const c = new Circle(1);
console.log('The radius is: ', c.draw());
7

Thanks, it did work. I don’t understand why the console.log in the draw method worked for Mosh in his video, but not for me and I copied his code verbatim?

8

Are you doing this in the Chrome console? You may need to select “user messages” on the left.

console

9

Thanks, I wasn’t aware of that option