Arrow functions and lexical this

babel_output_arrow_function_in_es_5.js

"use strict";

var Person = function Person(name, age, sex, friends) {
  var self = this !== undefined ? this : Object.create(Person.prototype);
  self.Name = name;
  self.Age = age;
  self.Sex = sex;
  self.Friends = friends;
  self.SayHelloToMyFriends = function () {
    var _this = this;

    this.Friends.forEach(function (f) {
      return console.log(_this.Name, "says hello to", f);
    });
  };
  return self;
};

var threeIdiots = [new Person("Mark", "25", "F", ["zorg", "xorg", "xergc"]), new Person("Arthur", "25", "F", ["lancelot", "boastalot", "talkalot"]), new Person("Trump", "35", "F", ["ed", "edd", "eddy"])];

threeIdiots.forEach(function (person) {
  person.Friends.forEach(function (x) {
    return console.log(person.Name, "has a friend named", x);
  });
  person.SayHelloToMyFriends();
});

es_2015_arrow_functions_and_lexical_this.js

var Person = function(name, age, sex, friends) {
  var self = this !== undefined ? this : Object.create(Person.prototype);
  self.Name = name;
  self.Age = age;
  self.Sex = sex;
  self.Friends = friends;
  self.SayHelloToMyFriends = function(){
    this.Friends.forEach(f => console.log(this.Name, "says hello to", f));
  };
  return self;
};

var threeIdiots = [
  new Person("Mark", "25", "F", ["zorg", "xorg", "xergc"]),
  new Person("Arthur", "25", "F", ["lancelot", "boastalot", "talkalot"]),
  new Person("Trump", "35", "F", ["ed", "edd", "eddy"])
];

threeIdiots.forEach(person => {
  person.Friends.forEach(x => console.log(person.Name, "has a friend named", x));
  person.SayHelloToMyFriends();
});

output.txt

Mark has a friend named zorg
Mark has a friend named xorg
Mark has a friend named xergc
Mark says hello to zorg
Mark says hello to xorg
Mark says hello to xergc
Arthur has a friend named lancelot
Arthur has a friend named boastalot
Arthur has a friend named talkalot
Arthur says hello to lancelot
Arthur says hello to boastalot
Arthur says hello to talkalot
Trump has a friend named ed
Trump has a friend named edd
Trump has a friend named eddy
Trump says hello to ed
Trump says hello to edd
Trump says hello to eddy