Event Bus Module

eventBus.js

var EventBus = (function(){
  "use strict";

  var subscriptions = {};
  var getNextUniqueId = getIdGenerator();


  var Bus = {
    subscribe: function(eventType, callback) {
      var id = getNextUniqueId();
      if(!subscriptions[eventType])
          subscriptions[eventType] = {};

      subscriptions[eventType][id] = callback;

      return { 
        unsubscribe: function() {
            delete subscriptions[eventType][id]
            if(Object.keys(subscriptions[eventType]).length === 0) {
              delete subscriptions[eventType];
            }
        }
      }
    },

    publish: function(eventType, arg) {
        if(!subscriptions[eventType])
            return

        Object.keys(subscriptions[eventType]).forEach(function(key) { 
              subscriptions[eventType][key](arg);
        });
    }
  }

  function getIdGenerator() {
    var lastId = 0
    
    return function getNextUniqueId() {
        lastId += 1
        return lastId
    }
  }
  
  return {
      subscribe: Bus.subscribe,
      publish: Bus.publish
  }
  
})();

var subscription1 = EventBus.subscribe(
  "print", function(message) {
    console.log('printing: '+ message);
});

var subscription2 = EventBus.subscribe(
  "add", function(mynums) {
    console.log(add(mynums[0],mynums[1]));
});

// App Code

// single addition fx
function add(a,b) {
  return a + b;
}

function doSomething() {
  console.log("doSomething");
  console.log("Hello!");
  EventBus.publish("add", [10, 5]);
  console.log("World");
}

function doSomethingElse() {
  console.log("doSomethingElse");
  console.log("Hi!");
  EventBus.publish("print", "Here is something to print, that is a little longer!");
  console.log("Bye");
}

//Implementation
doSomething();
doSomethingElse();

//end of App
subscription1.unsubscribe();
subscription2.unsubscribe();

/* Output
"doSomething"
"Hello!"
15
"World"
"doSomethingElse"
"Hi!"
"printing: Here is something to print, that is a little longer!"
"Bye"
*/