Using a class' Constructor function to initialise another class

Question

While refactoring a piece of code, I came across a class that I want to replace with a generic one. Hence, it should have pretty much the same functionality, but according to a "type" argument.

In order to ensure backward compatibility I don't want to just create a new class, but to keep the initialisations of the older one.

However I'm not sure how to implement this structure in JavaScript:

class Generic {
  constructor(type, data) {
    this.type = type;
    this.data = data;
  }

  action() {
    switch(this.type) {
      // Does things dynamically, depending on `this.type`
      case 'old': return `old: ${this.data}`;
      default: return this.data;
    }
  }
}

class Old {
  constructor(data) {
    // I want this to be equivalent to:
    // new Generic('old', data);
  }
}

// So this should work seamlessly
const foo = new Old('Hello');
const output = foo.action();
console.log(output);

Jonas Wilms · Accepted Answer · 2020-04-26 10:27:15Z

1

You could extend Generic:

  class Old extends Generic {
    constructor() {
       super("old");
   }
 }

answered Apr 26, 2020 at 10:27

Jonas Wilms

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