滚动条滚动，将table的head 实现fixed 利于多条数据查看

export function rollTable() {
  const dom = document.querySelector('.app-main')
  const table = document.querySelector('.el-table')
  const maxAsyncHeight = document.querySelector('.el-table').offsetTop
  dom.removeEventListener('scroll', resetFix)
  function resetFix() {
    const h = dom.scrollTop
    const tar = h - maxAsyncHeight
    if (tar > 40) {
      const elements = document.querySelectorAll('.newhead')
      elements.forEach(element => element.remove())
      const cloneHead = table.cloneNode(true)
      cloneHead.querySelector('.el-table__body-wrapper').remove()
      cloneHead.classList.add('newhead')
      dom.appendChild(cloneHead)
      cloneHead.style.position = 'fixed'
      cloneHead.style.top = '50px'
      cloneHead.style['z-index'] = 999
      cloneHead.style.left = '250px'
    } else {
      const elements = document.querySelectorAll('.newhead')
      elements.forEach(element => element.remove())
    }
  }
  dom.addEventListener('scroll', resetFix)
}