function removeClass (elem, ...classes) {
  let cls = elem.className || ''
  if (!cls || typeof cls !== 'string') {
    return
  }
  cls = '  ' + cls.split(/\s+/).join('  ') + '  '
  const clst = classes.join(' ').split(/\s+/)
  const reg = new RegExp(' ' + clst.join(' | ') + ' ', 'g')
  cls = cls.replace(reg, '')
    .replace(/^\s+|\s+$/g, '')
    .replace(/ {2,}/g, ' ')

  elem.className = cls
}
remove css class
@param elem
@param classes