dispatch(eventName, event) {
    const handlers = [].concat(this.eventHandlers[eventName] || []);
    for (const handler of handlers) {
      handler(event);
    }
    const nextHandlers = [].concat(this.nextEventHandlers[eventName] || []);
    for (const nextHandler of nextHandlers) {
      nextHandler(event);
    }
    delete this.nextEventHandlers[eventName];
    return true;
  }
Executes all events in the order they were added, with .on() event handlers executing before .onNext() handlers
@param {string} eventName
@param {any} event
@returns {true}