2 - Object Oriented Programming

1.js

class Counter {
  constructor(i = 0) {
    // this.counter = 999
    this._count = i
  }

  addOne() {
    this._count++
  }
  
  getCounter () {
    return this._count
  }

  setCounter(i) {
    if(typeof i !== 'number') {
      throw new Error('new counter value is not a number')
    }
    this._count = i;
  }
  
  get counter() {
    return this._count
  }
  
  set counter(i) {
    console.log(i)
    if(typeof i !== 'number') {
      throw new Error('new counter value is not a number')
    }
    this._count = i;
  }
  
  double() {
    this._count = this._count * 2
    return this._count
  }
}

const a = new Counter(3)
a.counter = 10
console.log(a.counter)

// a.addOne()
// a.setCounter(3)
// a.addOne()
// a.addOne()

// a.count = 0
// console.log(a.count)

// a.double()
// console.log(a.getCounter())

2.js

//another counter
//approach will be discussed on next lesson

function Counter(i=0) {
  let count = 0
  function increase() {
    count++
  }
  function decrease() {
    count--
  }
  function getCount() {
    return count
  }
  return ({
    increase,
    decrease,
    getCount
  })
}

const c = Counter()
c.increase()
c.increase()
c.decrease()
console.log(c.getCount())

3.js

class Rectangle {
  constructor(width, height) {
    this._width = width;
    this._height = height
  }

  getArea() {
    return this._width * this._height
  }
}

class Square {
  constructor(width) {
    this._width = width
  }

  getArea() {
    return this._width * this._width
  }
}

class Circle {
  constructor(radius) {
    this._radius = radius
  }

  getArea() {
    return Math.PI * this._radius ^ 2
  }
}

class AreaCalc {
  constructor() {
    this._figures = []
  }

  addFigure(figure) {
    if (!figure) {
      return
    }
    this._figures.push(figure)
  }

  getFigures() {
    return this._figures
  }

  area() {
    const result = this._figures.reduce((acc, i) => {
      if (i.getArea && typeof i.getArea === 'function') {
        return acc + i.getArea()
      } else {
        return acc
      }

    }, 0)
    return result
  }
}

class Triangle {

  constructor(a, b, c) {
    this._a = a;
    this._b = b;
    this._c = c;
    this.getArea = 5
  }

}

const rect = new Rectangle(2, 5)
const square = new Square(3)
const circle = new Circle(2)
const triangle = new Triangle(1, 2, 3)

const calc = new AreaCalc()
calc.addFigure(rect)
calc.addFigure(square)
calc.addFigure(circle)
calc.addFigure(triangle)

console.log(calc.area())

4.js

//abstraction & inheritance
class AbstractFigure {

  getType() {
    'Geometric Figure'
  }

  getArea() {
    return 0
  }

  render() {
    throw new Error('cant use abstract method') 
  }
}
// const aF = new AbstractFigure()

class Rectangle extends AbstractFigure {
  constructor(width, height) {
    super()
    this._width = width;
    this._height = height
  }

  getArea() {
    return this._width * this._height
  }

  render() {
    console.log('reactangle on screen')
  }
}

class Square  extends AbstractFigure{
  constructor(width) {
    super()
    this._width = width
  }

  getArea() {
    return this._width * this._width
  }
  render() {
    console.log('square on screen')
  }
}

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

  getArea() {
    return Math.PI * this._radius ^ 2
  }
}

class AreaCalc {
  constructor() {
    this._figures = []
  }

  addFigure(figure) {
    if (!figure) {
      return
    }
    this._figures.push(figure)
  }

  getFigures() {
    return this._figures
  }

  area() {
    const result = this._figures.reduce((acc, i) => {
      
      
      return acc + i.getArea()
    }, 0)
    return result
  }
}

class Triangle extends AbstractFigure {
  constructor(a, b, c) {
    super()
    this._a = a;
    this._b = b;
    this._c = c;
  }
}

class Display {
  constructor(items) {
    this._items = items;
    this._items.forEach(i => i.render())
  }
}

const rect = new Rectangle(2, 5)
const square = new Square(3)
const circle = new Circle(2) 
const triangle = new Triangle(1, 2, 3)

const calc = new AreaCalc()
 calc.addFigure(rect)
calc.addFigure(square)
calc.addFigure(circle) 
calc.addFigure(triangle)

console.log(triangle.getArea())

const d = new Display([rect, square])
//const d = new Display([rect, square, triangle]) //triangle will throw error
// console.log(calc.area())