Builder.js

class House {
  constructor() {
    this.walls = null;
    this.roof = null;
    this.pool = null;
    this.garden = null;
    this.internet = null;
  }

  setWalls(walls) {
    this.walls = walls;
  }

  setRoof(roof) {
    this.roof = roof;
  }

  setPool(pool) {
    this.pool = pool;
  }

  setGarden(garden) {
    this.garden = garden;
  }

  setInternet(internet) {
    this.internet = internet;
  }
}

class HouseBuilder {
  constructor() {
    this.house = new House();
  }

  buildWalls(walls) {
    this.house.setWalls(walls);
    return this; // returning this for method chaining
  }

  buildRoof(roof) {
    this.house.setRoof(roof);
    return this;
  }

  buildPool(pool) {
    this.house.setPool(pool);
    return this;
  }

  buildGarden(garden) {
    this.house.setGarden(garden);
    return this;
  }

  getHouse() {
    const house = this.house;
    this.reset();
    return house;
  }

  reset() {
    this.house = new House();
  }
}

const house = builder
  .buildWalls(4)
  .buildRoof('sloped')
  .buildGarden(['trees', 'grass', 'peacocks'])
  .getHouse();