Xto6 modernizes your JavaScript code(xto6.js.org)

  const x = function () {};

  x.prototype.a = wrapFunction(function(){});

  class x {
     a() wrapFunction(function(){}); // invalid :-(
  }

  var x = function () {};
  x.prototype.a = <foo>;

  var x = () => {};
  x.prototype.a = <foo>; // cannot set a of undefined

  Person.prototype.getAge = function (birthYear) {
    var age = 2015;
    age -= birthYear;

    return result;
    // Do you mean return age?
  };

  Object.defineProperty(Person.prototype, 'age', {
    get: function () {
      return this.getAge();
      // getAge function takes a required parameter.
    }
  });

    var Person = function (name) {
      console.log('This is the constructor.');

      var _name = name;

      this.getName = function() {
          return _name;
      };
    };