class

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); 
    } 
  } 
  
  //create class
  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 Animal = function () {
  function Animal(name) {
    _classCallCheck(this, Animal);

    this.name = name;
  }

  _createClass(Animal, [{
    key: 'speak',
    value: function speak() {
      console.log(this.name + ' makes a noise.');
    }
  }]);

  return Animal;
}();

var Dog = function (_Animal) {

  _inherits(Dog, _Animal);

  function Dog() {
    _classCallCheck(this, Dog);

    return _possibleConstructorReturn(this, Object.getPrototypeOf(Dog).apply(this, arguments));
  }

  _createClass(Dog, [{
    key: 'speak',
    value: function speak() {
      console.log(this.name + ' barks.');
    }
  }]);

  return Dog;
}(Animal);

http://jsbin.com/zayoro/1/