用户离开 / 用户进来

// 监听用户进来 或 用户出去
      let vE = 'visibilitychange'
      if(document.webkitHidden != 'undefined') { //兼容
        vE = 'webkitvisibilitychange'
      }

      function visibilityChanged() {
        if(document.hidden || document.webkitHidden) {
          console.log('user is leave:' + new Date())
        } else {
          console.log('user is use:' + new Date())
        }
      }

      document.addEventListener(vE, visibilityChanged, false)