Method on

src/lib/EventHandler.js:185–190

* The new event handling style to asign a function to an event. * @param {String} event The event descriptor * @param {Function} handler The event handler

(event, handler)

   * @param  {Function} handler   The event handler
   */
  on(event, handler) {
    if (!event || typeof event !== 'string' || event === '_reply' || typeof handler !== 'function') {
      throw new Error('Invalid event handler!');
    }
    this._handlers.set(event, handler.bind(this._handlerObject || this));
  }

  /**
   * Helper to emit events via postMessage using a port.