Function on

src/core/events-emitter.ts:9–24

(
    this: Swiper,
    events: keyof SwiperEvents | string,
    handler: SwiperEventHandler,
    priority?: boolean,
  )

export default {
  on(
    this: Swiper,
    events: keyof SwiperEvents | string,
    handler: SwiperEventHandler,
    priority?: boolean,
  ): Swiper {
    const self = this;
    if (!self.eventsListeners || self.destroyed) return self;
    if (typeof handler !== 'function') return self;
    const method: 'unshift' | 'push' = priority ? 'unshift' : 'push';
    (events as string).split(' ').forEach((event) => {
      if (!self.eventsListeners[event]) self.eventsListeners[event] = [];
      self.eventsListeners[event]![method](handler);
    });
    return self;
  },

  once(
    this: Swiper,