2_O.js

// Open Close Principle

class Shape {
  area() {
    throw new Error('Area method should be implemented')
  }
}

class Square extends Shape {
  constructor(size) {
    super()
    this.size = size
  }

  area() {
    return this.size ** 2
  }
}

class Circle extends Shape {
  constructor(radius) {
    super()
    this.radius = radius
  }

  area() {
    return (this.radius ** 2) * Math.PI
  }
}

class Rect extends Shape {
  constructor(width, height) {
    super()
    this.width = width
    this.height = height
  }

  area() {
    return this.width * this.height
  }
}

class Triangle extends Shape {
  constructor(a, b) {
    super()
    this.a = a
    this.b = b
  }

  area() {
    return (this.a * this.b) / 2
  }
}

class AreaCalculator {
  constructor(shapes = []) {
    this.shapes = shapes
  }

  sum() {
    return this.shapes.reduce((acc, shape) => {
      acc += shape.area()
      return acc
    }, 0)
  }
}


const calc = new AreaCalculator([
  new Square(10),
  new Circle(1),
  new Circle(5),
  new Rect(10, 20),
  new Triangle(10, 15)
])

console.log(calc.sum())