A basic gist illustrating the use of ES6 classes compared to ES5. https://medium.com/@philipaffulnunoo/migrating-to-es6-classes-67800de0d2a2

class.js

class Car {
  constructor(number_of_wheels, number_of_doors) {
    this.number_of_wheels = number_of_wheels;
    this.number_of_doors  = number_of_doors;
  }
  getCarInfo() {
    return this.number_of_wheels + ' wheels, ' + this.number_of_doors + ' doors.';
  }
}

class Tesla extends Car{
  constructor(number_of_wheels, number_of_doors, battery_size) {
    super(number_of_wheels, number_of_doors)
    this.battery_size = battery_size
    this._weight = 100
  }
  
  getCarInfo() {
    return super.getCarInfo() + " A Tesla model with " + this.battery_size + " batteries."
  }
  
  get weight () {
    return this._weight
  }
  
  set weight (weight) {
    this._weight = weight
  }
}

let tesla = new Tesla(4,2, 5)
console.log("size", tesla.weight) // weight is 100
tesla.weight = 20 
console.log("size", tesla.weight) // weight is now 20

class_2.js

'use strict';

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Car = function () {
  function Car(number_of_wheels, number_of_doors) {
    _classCallCheck(this, Car);

    this.number_of_wheels = number_of_wheels;
    this.number_of_doors = number_of_doors;
  }

  Car.prototype.getCarInfo = function getCarInfo() {
    return this.number_of_wheels + ' wheels, ' + this.number_of_doors + ' doors.';
  };

  return Car;
}();

var Tesla = function (_Car) {
  _inherits(Tesla, _Car);

  function Tesla(number_of_wheels, number_of_doors, battery_size) {
    _classCallCheck(this, Tesla);

    var _this = _possibleConstructorReturn(this, _Car.call(this, number_of_wheels, number_of_doors));

    _this.battery_size = battery_size;
    _this._weight = 100;
    return _this;
  }

  Tesla.prototype.getCarInfo = function getCarInfo() {
    return _Car.prototype.getCarInfo.call(this) + " A Tesla model with " + this.battery_size + " batteries.";
  };

  _createClass(Tesla, [{
    key: 'weight',
    get: function get() {
      return this._weight;
    },
    set: function set(weight) {
      this._weight = weight;
    }
  }]);

  return Tesla;
}(Car);

var tesla = new Tesla(4, 2, 5);
console.log("size", tesla.weight); // weight is 100
tesla.weight = 20;
console.log("size", tesla.weight); // weight is now 20