classes.js

'use strict'
class Animal {
  constructor (name) {
    this.name = name
  }

  walk () {
    console.log(`${this.name} is walking`)
  }
}

class Rabbit extends Animal {
  walk () {
    super.walk()
    console.log("...and jumping!")
  }
}

new Animal('John').walk()
new Rabbit('Bob').walk()