intersection observers with callback

intersection-observers.ts

export type Callback = (
  entry: IntersectionObserverEntry,
  observer: IntersectionObserver,
) => void

const opts = { threshold: 0 }
const observer = new IntersectionObserver(
  (entries, ob) => {
    entries.forEach((entry) => {
      entry.target.classList.toggle("__is-intersecting", entry.isIntersecting)
      map.get(entry.target)(entry, ob)
    })
  },
  opts
)

const map = new WeakMap<Element, Callback>()

export function observeIntersection(el: Element, cb: Callback) {
  map.set(el, cb)
  observer.observe(el)
  //console.log(el, cb)
}