ES6 static menber

class Tripple {
  static tripple(n) {
    n = n || 1;
    return n * 3;
  }
}

class BiggerTripple extends Tripple {
  static tripple(n) {
    return super.tripple(n) * super.tripple(n);
  }
}

console.log(Tripple.tripple());//3
console.log(Tripple.tripple(6));//18
console.log(BiggerTripple.tripple(3));//81

Class inheritance

class Shape {
  constructor(id,x, y){
    this.id = id;
    this.move(x,y);
  }
  move(x, y){
    this.x  = x;
    this.y = y;
  }
}

class Rectangle extends Shape {
  constructor(id, x, y, width, height){
    super(id, x, y);
    this.width = width;
    this.height = height;
  }
  getWidth(){
    return this.width * this.height
  }
}

class Radius extends Shape {
  constructor(id, x, y, radius){
    super(id, x, y);
    this.radius = radius;
  }
  getRudius(){
    return 10 * this.radius;
  }
}
var rec = new Rectangle(1,10,12,100,50);
console.log(rec.getWidth());

var radius = new Radius(2,20,12,50);
console.log(radius.getRudius());

code

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