front-proposal.js

class Front {
  async initialize() {
    throw new Error("initialize Mandatory");
  }

  static async createFront() {
    const front = new this();
    await front.initialize(); 
    return front;
  }
}

class FrontA extends Front {
  async initialize() {
    await new Promise(r => setTimeout(r, 100));
    this._prop = 42;
    this._Aprop = 42;
  }
}

class FrontB extends FrontA {
  async initialize() {
    await super.initialize(); 
    await new Promise(r => setTimeout(r, 100));
    this._prop = 43;
    this._BProp = 43;
  }
}

var a = await FrontA.createFront();
var b = await FrontB.createFront();
console.log(a, b)