Function normalizeContainer

packages/runtime-dom/src/index.ts:234–257

(
  container: Element | ShadowRoot | string,
)

}

function normalizeContainer(
  container: Element | ShadowRoot | string,
): Element | ShadowRoot | null {
  if (isString(container)) {
    const res = document.querySelector(container)
    if (__DEV__ && !res) {
      warn(
        `Failed to mount app: mount target selector "${container}" returned null.`,
      )
    }
    return res
  }
  if (
    __DEV__ &&
    window.ShadowRoot &&
    container instanceof window.ShadowRoot &&
    container.mode === 'closed'
  ) {
    warn(
      `mounting on a ShadowRoot with \`{mode: "closed"}\` may lead to unpredictable bugs`,
    )
  }
  return container as any
}

// Custom element support
export {