text: import { forEach } from './utils'
  /**
   * 监听document.body.childNode变化
   * @private
   * @function
   */
  export const observe = () => {
    const observer = new MutationObserver(mutationsList => {
      forEach(mutationsList, mutation => {
        forEach(mutation.removedNodes, node => { node.$isUpdate = false })
        forEach(mutation.addedNodes, node => { node.$isUpdate = true })
      })
    })
    observer.observe(document.body, { childList: true, subtree: true })
  }
  