Function whenAvailable

packages/utils/src/index.ts:860–877

(
  childId: string,
  callback: (el: Element) => void,
  root?: Document | ShadowRoot
)

 * @public
 */
export function whenAvailable(
  childId: string,
  callback: (el: Element) => void,
  root?: Document | ShadowRoot
): void {
  if (!isBrowser) return
  if (!root) root = document
  const el = root.getElementById(childId)
  if (el) return callback(el)
  const observer = new MutationObserver(() => {
    const el = root?.getElementById(childId)
    if (el) {
      observer?.disconnect()
      callback(el)
    }
  })
  observer.observe(root, { childList: true, subtree: true })
}

/**
 * Given a function only 1 call will be made per call stack. All others will