EventManager

EventManager.js

var EventManager = function() {
  var emitter = this;

  // Map of even names to list of event callbacks
  emitter.events = {};
};

/*
  Registerer a callback function for a specific event
 */
EventManager.prototype.on = function(name, fn) {
  var emitter = this;

  if (typeof name !== 'string') {
    throw 'event name must be a string';
  }

  var events = emitter.events[name];
  if (!events) {
    // Init the events for this event type
    events = [fn];
    emitter.events[name] = events;
  } else {
    if (events.indexOf(fn) === -1) {
      events.push(fn);
    }
  }
};

/*
  Removes a registered callback function for a specific event
 */
EventManager.prototype.off = function(name, fn) {
 var emitter = this;

  if (typeof name !== 'string') {
    throw 'event name must be a string';
  }

  var events = emitter.events[name];
  if (events) {
    var index = events.indexOf(fn);
    if (index !== -1) {
      events.splice(index, 1);
      if (!events.length) {
        delete emitter.events[name];
      }
    }
  }
};

/*
  Call all callback functions for the registered event.
  Passing any additional parameters after the eventName
    to the callback functions
 */
EventManager.prototype.emit = function(name) {
  var emitter = this;
  var args = Array.prototype.slice.call(arguments, 1);

  if (typeof name !== 'string') {
    throw 'event name must be a string';
  }

  // Get registered callbacks for the event name
  var events = emitter.events[name];
  if (events) {
    events.forEach(function(fn) {
      try {
        // Run the callback passing in the additional attributes
        fn.apply(fn, args);
      } catch (e) {
        console.error(e);
      }
    });
  }
};