如何在React項目中添加Service Worker

Question

我想在我的React項目中添加Service Worker。 項目已准備就緒，默認服務似乎無法正常工作。

即使當我嘗試導入它時，它也會出現此錯誤：

嘗試導入錯誤：“ ./ registerServiceWorker”不包含默認導出（導入為“ registerServiceWorker”）。

此外，如何在默認版本的serviceWorker文件中添加要緩存的文件。

如果我像無反應（框架）應用程序一樣添加自己的自定義serviceWorker文件，它將適用於反應情況嗎？

目前，我的index.js中有這些代碼

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import registerServiceWorker from './registerServiceWorker';


import { BrowserRouter } from 'react-router-dom'

ReactDOM.render(
    <BrowserRouter>
        <App />
    </BrowserRouter>,
document.getElementById('root'));

registerServiceWorker();

並且這樣說：“嘗試導入錯誤：'./ registerServiceWorker'不包含默認導出（導入為'registerServiceWorker'）。”

我正在使用的Service Worker如下：（React的默認代碼）

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) {
    if (process.env.NODE_ENV === 'production' && '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

        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,  
            );
          });
        } 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  /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();
      });
    }
  }

Answer 1

根據您的錯誤信息，registerServiceWorker.js文件存在問題。

import registerServiceWorker from './registerServiceWorker';

但是，registerServiceWorker.js文件中沒有以下內容

export registerServiceWorker

因此，我建議將以下內容添加到registerServiceWorker.js

export default registerServiceWorker

---

編輯：

用這個來導入js文件

import * as registerServiceWorker from './registerServiceWorker';

並像這樣使用它：

registerServiceWorker.unregister();

---

EDIT2：

我認為您對導入/導出有一些誤解，因此我將在此進行解釋。

如果我們想將某個文件（例如child.js）導入另一個文件（例如parent.js）。在child.js之類的文件中，必須進行導出。

有一些方法可以做到這一點。 1.在Child.js中

const child = () => {

}
export default Child

我們可以像下面這樣將其導入parent.js中，使用默認表達式，我們實際上可以在下面的Child位置使用任何名稱（通常保持不變）。

import Child from './child.js'
import ChildReplace from './child.js' //This also works, the ChildReplace are actually the Child in the child.js

---

2. 您可能會看到另一種導入方式，例如：

   從'./registerServiceWorker'導入*作為registerServiceWorker；

*表示registerServiceWorker.js。“ as registerServiceWorker”中的所有內容都為所有內容命名，以便我們輕松導入。

導入文件的方法，因為在registerServiceWorker.js中，有許多導出表達式，但是沒有導出默認值。

Answer 2

您可以使用導入從registerServiceWorker.js文件導出的所有功能

從'./registerServiceWorker'導入*作為registerServiceWorker；

然后，您可以從該文件調用任何方法到index.js文件，例如-

registerServiceWorker.unregister（）;

Answer 3

嘗試這個。

create-react-app FolderName

只是自動為您的應用程序創建一個registerServiceWorker