builder.js

class Point {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
}

class PointBuilder {

  constructor() {
    this.x = 0;
    this.y = 0;
  }
  
  setX(x) {
    this.x = x;
  }
  
  setY(y) {
    this.y = y;
  }
  
  build() {
    return new Point(x, y);
  }
}