Method fire

src/core/data-structures/observable.js:57–65

* Fires an event. All observers are called. * @param {TYPE=} opt_event

(opt_event)

   * @param {TYPE=} opt_event
   */
  fire(opt_event) {
    if (!this.handlers_) {
      return;
    }
    // Iterate over copy of handlers_ in case handlers are removed inside.
    for (const handler of this.handlers_.slice()) {
      handler(opt_event);
    }
  }

  /**
   * Returns number of handlers. Mostly needed for tests.