SOURCE

    async function iKonwYouVisitedTheWebsite(resourceSrc){
      function getLoadTime(){
        return new Promise(r=>{
          const script = document.createElement('script')
          const start = Date.now()
          script.onload = () => {
            document.body.removeChild(script)
            r(Date.now() - start)
          }
          script.src = resourceSrc
          document.body.appendChild(script)
        })
      }
      const t1 = await getLoadTime()
      const t2 = await getLoadTime()
      return t1 - t2
    }
 
  
  iKonwYouVisitedTheWebsite('https://static.zhihu.com/heifetz/main.app.a662d8a4162fcbc4916e.js').then(t=>{
    document.write(t>250 ? `您没上过知乎:${t}` : `您上过知乎:${t}`)
  })