Function observe

packages/next/src/client/use-intersection.tsx:69–94

(
  element: Element,
  callback: ObserveCallback,
  options: UseIntersectionObserverInit
)

}

function observe(
  element: Element,
  callback: ObserveCallback,
  options: UseIntersectionObserverInit
): () => void {
  const { id, observer, elements } = createObserver(options)
  elements.set(element, callback)

  observer.observe(element)
  return function unobserve(): void {
    elements.delete(element)
    observer.unobserve(element)

    // Destroy observer when there's nothing left to watch:
    if (elements.size === 0) {
      observer.disconnect()
      observers.delete(id)
      const index = idList.findIndex(
        (obj) => obj.root === id.root && obj.margin === id.margin
      )
      if (index > -1) {
        idList.splice(index, 1)
      }
    }
  }
}

export function useIntersection<T extends Element>({
  rootRef,