service-worker.tsx

// This optional code is used to register a service worker.
// register() is not called by default.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on subsequent visits to a page, after all the
// existing tabs open on the page have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read https://bit.ly/CRA-PWA

const isLocalhost = Boolean(
    window.location.hostname === "localhost" ||
      // [::1] is the IPv6 localhost address.
      window.location.hostname === "[::1]" ||
      // 127.0.0.1/8 is considered localhost for IPv4.
      window.location.hostname.match(
        /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
      )
  )

export function register(config?: any) {
    if (process.env.NODE_ENV === "prsoduction" && "serviceWorker" in navigator) {
      // The URL constructor is available in all browsers that support SW.
      const publicUrl = new URL(
        (process).env.PUBLIC_URL || "",
        window.location.href
      )
      if (publicUrl.origin !== window.location.origin) {
        // Our service worker won't work if PUBLIC_URL is on a different origin
        // from what our page is served on. This might happen if a CDN is used to
        // serve assets; see https://github.com/facebook/create-react-app/issues/2374
        return
      }

      window.addEventListener("load", () => {
        const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`

        if (isLocalhost) {
          // This is running on localhost. Let's check if a service worker still exists or not.
          checkValidServiceWorker(swUrl, config)

          // Add some additional logging to localhost, pointing developers to the
          // service worker/PWA documentation.
          navigator.serviceWorker.ready.then(() => {
            console.log(
              "This web app is being served cache-first by a service " +
                "worker. To learn more, visit https://bit.ly/CRA-PWA"
            )
          })
        } else {
          // Is not localhost. Just register service worker
          registerValidSW(swUrl, config)
        }
      })
    }
  }

function registerValidSW(swUrl, config) {
    navigator.serviceWorker
      .register(swUrl)
      .then((registration) => {
        registration.onupdatefound = () => {
          const installingWorker = registration.installing
          if (installingWorker == null) {
            return
          }
          installingWorker.onstatechange = () => {
            if (installingWorker.state === "installed") {
              if (navigator.serviceWorker.controller) {
                // At this point, the updated precached content has been fetched,
                // but the previous service worker will still serve the older
                // content until all client tabs are closed.
                console.log(
                  "New content is available and will be used when all " +
                    "tabs for this page are closed. See https://bit.ly/CRA-PWA."
                )

                // Execute callback
                if (config && config.onUpdate) {
                  config.onUpdate(registration)
                }
              } else {
                // At this point, everything has been precached.
                // It's the perfect time to display a
                // "Content is cached for offline use." message.
                console.log("Content is cached for offline use.")

                // Execute callback
                if (config && config.onSuccess) {
                  config.onSuccess(registration)
                }
              }
            }
          }
        }
      })
      .catch((error) => {
        console.error("Error during service worker registration:", error)
      })
  }

function checkValidServiceWorker(swUrl, config) {
    // Check if the service worker can be found. If it can't reload the page.
    fetch(swUrl)
      .then((response) => {
        // Ensure service worker exists, and that we really are getting a JS file.
        const contentType = response.headers.get("content-type")
        if (
          response.status === 404 ||
          (contentType != null && contentType.indexOf("javascript") === -1)
        ) {
          // No service worker found. Probably a different app. Reload the page.
          navigator.serviceWorker.ready.then((registration) => {
            registration.unregister().then(() => {
              window.location.reload()
            })
          })
        } else {
          // Service worker found. Proceed as normal.
          registerValidSW(swUrl, config)
        }
      })
      .catch(() => {
        console.log(
          "No internet connection found. App is running in offline mode."
        )
      })
  }

export function unregister() {
    if ("serviceWorker" in navigator) {
      navigator.serviceWorker.ready.then((registration) => {
        registration.unregister()
      })
    }
  }