class.prototype.js

function Animal(name) {
  this.name = name;
  this.speed = 0;
}

Animal.prototype.run = function(speed) {
  this.speed += speed;
  console.log(this.name + ' бежит, скорость ' + this.speed);
};

Animal.prototype.stop = function() {
  this.speed = 0;
  console.log(this.name + ' стоит');
};

function Rabbit(name) {
  Animal.apply(this, arguments);
  this.size = 100;
}

Rabbit.prototype = Object.create(Animal.prototype);
Rabbit.prototype.constructor = Rabbit;

Rabbit.prototype.jump = function() {
  this.speed++;
  console.log(this.name + ' прыгает');
};

// переопределим метод run()
Rabbit.prototype.run = function(speed) {
  Animal.prototype.run.apply(this, arguments);
  this.jump();
};

var rabbit = new Rabbit('Кроль');

console.log(rabbit);

rabbit.run(500);
rabbit.stop();
rabbit.jump();
console.log(rabbit.speed);