EventWaiter.js

/**
 * Wait for x events to finish, and then call a function.
 * @param {Array} ids [Registered event ids] 
 */
function EventWaiter(ids){
  if(names instanceof Array) {
    this.waitEvents = ids;
  }
}

EventWaiter.prototype = {
  waitEvents: [],
  callback: undefined,

  /**
   * Registry a new event
   * @param  {Anything} id [Id of the new event]
   * @return {bool}        [Existed already?]
   */
  registry: function(id){
    if(this.names.indexOf(id) == -1) {
      this.waitEvents.push(id);
      return false;   
    }
    return true;
  }

  /**
   * Called when a event finished
   * @param  {Anything} id [Id of the finished event]
   * @return {bool}        [Did the EventWaiter finished?]
   */
  call: function(id){
    remove(this.waitEvents, id);
    if(this.waitEvents.length <= 0 && this.callback){
      this.callback();
      this.callback = undefined;
      return true;
    }
    return false;
  },

  /**
   * Set the function to be called when the EventWaiter finishes
   * @param  {Function} callback
   */
  then: function(callback){
    this.callback = callback;
  },
}

function remove(array, element){
  var index = array.indexOf(element);
  if (index > -1) {
    array.splice(index, 1);
  }
}



// Example

eventWaiter = new EventWaiter(["bailar", "cantar", "comer"]);

bailar(function(){
  eventWaiter.call("bailar");
});

cantar(function(){
  eventWaiter.call("cantar");
});

comer(function(){
  eventWaiter.call("comer");
});

eventWaiter.then(function(){
  console.log("Finish");
});