// 網絡狀況

    class Network {

      // 有網絡的鉤子

      static observerOnline(func = () => {}) {

        Network.addHandler(window, 'online', func);

      }

      // 斷網的鉤子

      static observerOffline(func = () => {}) {

        Network.addHandler(window, 'offline', func);

      }

      static addHandler(elementParam, type, handler) {

        const element = elementParam;

        if (element.addEventListener) {

          element.addEventListener(type, handler, false);

        } else if (element.attachEvent) {

          element.attachEvent(`on${type}`, handler);

        } else {

          element[`on${type}`] = handler;

        }

      }

    }

    // 監聽有網的情況

    Network.observerOnline(() => {

      const isRefresh = confirm('網絡已恢復正常，是否要刷新頁面?');

      if (isRefresh === true) {

        window.location.reload();

      }

    });

    // 監聽斷網的情況

    Network.observerOffline(() => {

      alert('目前已斷網，請檢查您的網絡鏈接。');

    });