CODEWITHSUNDEEP
ecmascript-6
Noitidart
Noitidart

Reputation: 37238

How to use this before super?

I know that this is not allowed before super but I need to do it. I was wondering if there was a legal way to do this in es6?

My code:

class DOMElement {
  constructor(aNodeName) {
    this.name = aNodeName;
    this.create();
  }
  create() {
    let domref = document.createElement(this.name);
    document.body.appendChild(domref);
    return domref;
  }
}

class Button extends DOMElement {
  constructor(aLabel) {
    this.label = aLabel;
    super('button');
  }
  create() {
    let domref = super.create();
    domref.textContent = this.label;
  }
}

If I don't set this.label before calling super('button') in Button.prototype.create then domref.textContent is set to undefined.

Upvotes: 0

Views: 610

Answers (1)

Estus Flask
Estus Flask

Reputation: 222369

There's no 'legal' way.

It can be be a getter in cases where static property value is supposed to be used by parent class on construction:

get label() {
  return 'label';
}

In this case this means that class design is just wrong. There's nothing in parent class that would impose such restriction. Actually, label is only used by child class. It should be:

  constructor(aLabel) {
    super('button');
    this._domref.textContent = alabel;
  }
  create() {
    // if parent class is user-defined, it should be done there
    // instead of returning a value, because it doesn't make sense
    // to leave an important part of the object without a reference
    this._domref = super.create();
  }

Upvotes: 2

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