text: function foo() {
      var ParentClass = function () {
          function ParentClass() {
          }
          ParentClass.prototype.f = function () {
              return 'hello world';
          };
          return ParentClass;
      }();
      var MyClass = function () {
          function MyClass() {
              ParentClass.apply(this, arguments);
          }
          MyClass.prototype = Object.create(ParentClass.prototype);
          return MyClass;
      }();
      var x = new MyClass('test');
      console.log(x.f());
  }
  
  foo();
  
  