工厂模式

class Point{
  constrcutor(x, y){
      this.x = x;
    this.y = y;
  }
    static newCartesianPoint(x, y){
      return new Point(x, y);
  }
  static newPolarPoint(rho, theta){
      return new Point(rho * Math.cos(theta), ro * Math.sin(theta);
  }
}