shapes.js

class Triangle {
  constructor(a, b, c, h) {
    this.a = a;
    this.b = b;
    this.c = c;
    this.h = h;
  }
  area() {
    return `Area: ${this.b} * ${this.h} / 2 = ${(this.b * this.h) / 2}`;
  }
  perimeter() {
    if ((this.a && this.c == null) || this.a == null || this.c == null) {
      return;
    } else {
      return `Perimeter: ${this.a} + ${this.b} + ${this.c} = ${
        this.a + this.b + this.c
      }`;
    }
  }
}

class Rectangle {
  constructor(h, w) {
    this.h = h;
    this.w = w;
  }
  area() {
    return `Area: ${this.h} * ${this.w} = ${this.h * this.w}`;
  }
  perimeter() {
    return `Perimeter: ${this.h} * 2 + ${this.w} * 2 = ${
      this.h * 2 + this.w * 2
    }`;
  }
}

class Square extends Rectangle {
  constructor(len) {
    // The parents (Rectangle) class's constructor function is called for the Rectangles height and width.
    // The super keyword is used here because the constructor for square is pretty much the same as rectangle.
    super(len, len);
  }
}

class Circle {
  constructor(r) {
    this.r = r;
  }
  radius() {
    return `Radius: ${Math.PI} * ${this.r}² = ${Math.PI * this.r ** 2}`;
  }
  circumference() {
    return `Circumference: ${Math.PI} * ${this.r} * 2 = ${
      Math.PI * this.r * 2
    }`;
  }
}