Is it possible to instantiate child class from a static method in base class [node JS]?

Question

I want to create an instance of child class from a static method in a base class

class Base {
  static find(id) {
    const attributes = database.get(id);
    return new getChildClass(attributes);
  }
}

class FirstChild extends Base {
}

class SecondChild extends Base {
}

I want FirstChild.find(1) to return an instance of FirstChild and SecondChild.find(1) to return an instance of SecondChild

Is in possible to achieve this in node JS?

score 2 · Accepted Answer · answered Mar 25 '19 at 23:49

2

When calling find from the child class, this inside find will refer to that child class, so you can just return new this from find:

class Base {
  static find(id) {
    const attributes = 'foo'; // database.get(id);
    return new this(attributes);
  }
}

class FirstChild extends Base {
}

class SecondChild extends Base {
}

console.log(FirstChild.find(1) instanceof FirstChild);
console.log(SecondChild.find(1) instanceof SecondChild);

answered Mar 25 '19 at 23:49

CertainPerformance

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Does anyone know how to achieve the same thing in typescript without it resulting in an error? – Jammer Feb 04 '21 at 01:24
@Jammer It looks to work fine in TS as-is, if you just add the type annotations when necessary – CertainPerformance Feb 04 '21 at 01:29

Is it possible to instantiate child class from a static method in base class [node JS]?

1 Answers1