Strategies and template methods

template_methods.js

// Since the GreetingStrategy#execute method uses methods to define its algorithm,
// the Template Method pattern, we can subclass it and simply override one of those
// methods to alter the behavior without changing the algorithm.

var PoliteGreetingStrategy = function() {};
PoliteGreetingStrategy.prototype = Object.create(GreetingStrategy.prototype);
PoliteGreetingStrategy.prototype.sayHi = function() {
  return "Welcome sir, ";
};

var FriendlyGreetingStrategy = function() {};
FriendlyGreetingStrategy.prototype = Object.create(GreetingStrategy.prototype);
FriendlyGreetingStrategy.prototype.sayHi = function() {
  return "Hey, ";
};

var BoredGreetingStrategy = function() {};
BoredGreetingStrategy.prototype = Object.create(GreetingStrategy.prototype);
BoredGreetingStrategy.prototype.sayHi = function() {
  return "sup, ";
};

var politeGreeter   = new Greeter(new PoliteGreetingStrategy());
var friendlyGreeter = new Greeter(new FriendlyGreetingStrategy());
var boredGreeter    = new Greeter(new BoredGreetingStrategy());

politeGreeter.greet();   //=> 'Welcome sir, Goodbye.'
friendlyGreeter.greet(); //=> 'Hey, Goodbye.'
boredGreeter.greet();    //=> 'sup, Goodbye.'