docs: function removeClass (el, className) {
    if (!className) return
  
    if (Array.isArray(className)) {
      each(className, function (className) {
        removeClass(el, className)
      })
  
      return
    }
  
    if (el.classList) {
      var classNames = className.split(' ').filter(Boolean)
      each(classNames, function (className) {
        el.classList.remove(className)
      })
    } else {
      var expr =
        new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi')
  
      el.className = el.className.replace(expr, ' ')
    }
  }