text: var filename = location.href.match(/[\w\.]+$/)
  window.addEventListener('DOMContentLoaded', function () {
      var rate = localStorage.getItem(filename)
      var sh = document.body.scrollHeight
      document.body.scrollTop = sh * Number(rate)
      window.addEventListener('scroll', function (e) {
          var sh = document.body.scrollHeight,
              st = document.body.scrollTop
          localStorage.setItem(filename, st / sh)
      })
  })