Дождаться отображение элемента

function waitForElm(selector:string): Promise<HTMLElement> {
  return new Promise<HTMLElement>(resolve => {
    const element = document.querySelector(selector) as HTMLElement
    if (element) return resolve(element)

    const observer = new MutationObserver(() => {
      const element = document.querySelector(selector) as HTMLElement
      if (!element) return
      observer.disconnect()
      resolve(element)
    })

    observer.observe(document.body, {childList: true, subtree: true})
  })
}