Social media example using this

friend.js

// Constructor Function
var Friend = function(name, password, interests, job){
  this.fullName = name;
  this.password = password;
  this.interests = interests;
  this.job = job;
};

function sayHello(){
   // uncomment the console.log to see the object that 'this' points to
  //  console.log(this); 
  return `Hi, my name is ${this.fullName} and I'm a ${this.job}. Let's be friends!`;
}

// Create one or multiple instances of the Friend prototype with the keyword 'new'
var john = new Friend('John Smith', 'badpassword', ['hiking', 'biking', 'skiing'], 'teacher'); 

console.log(john); 

// Assign the function to the greeting key on the john object
john.greeting = sayHello; 

// Call the the new method
console.log( john.greeting() ); 

// Remember, you can't call sayHello() as a function; it will return "Hi, my name is undefined and I'm a undefined. Let's be friends!"
// Because the function's context is global and the window object does NOT have the keys that belong to the Friend prototype
console.log( sayHello() ) ;