factory.ts

class Circle {
  radius: number;
  constructor(radius: number) {
    this.radius = radius;
  }
}

class Square {
  sideLength: number;
  constructor(sideLength: number) {
    this.sideLength = sideLength;
  }
}

enum ShapeType {
  Circle,
  Square,
}

class ShapeFactory {
  static createShape(type: ShapeType, param: number): Circle | Square {
    switch (type) {
      case ShapeType.Circle:
        return new Circle(param);
      case ShapeType.Square:
        return new Square(param);
    }
  }
}

const circle = ShapeFactory.createShape(ShapeType.Circle, 10);
console.log(circle.radius); // 10

const square = ShapeFactory.createShape(ShapeType.Square, 20);
console.log(square.sideLength); // 20