找不到模块：使用 React Router 时无法解析“./serviceWorker”

Question

我收到此错误：找不到模块：无法解析“/home/radu/Desktop/ReactAppStudents/barbut/src”中的“./serviceWorker”

这是我的 index.js 文件。

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import * as serviceWorker from "./serviceWorker";
import { BrowserRouter as BrowserRouter} from "react-router-dom";


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

//reportWebVitals();
serviceWorker.unregister();

这是我尝试使用 React Router 的 App.js。

import React from 'react';
import {BrowserRouter , Switch, Route } from "react-router-dom";

import Login from "./Login";
import SignUp from "./SignUp";

function App() {
  return (
  <div>
    <BrowserRouter>
      <Switch>
        <Route exact path={"/"} component={() => <h1>Index</h1>} />
        <Route path={"/login"} component={()=> <h1>Login</h1>} />
        <Route path={"/home"} component={<h1>Home</h1>} />
        </Switch>
    </BrowserRouter>
    </div>
  );
}

export default App;

Answer 1

创建文件名 serviceWorker.js

src/serviceWorker.js

使用这些代码

// 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

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
      // 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'
          );
        });
      } 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 '
              );

              // 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 2

如果您使用 create-react-app 版本 4+ 创建了应用程序，则默认项目模板已更改，并且 service worker 现在已选择加入，并且默认情况下不再包括在内。

因此，只需从 index.js 中删除对 serviceWorker 的任何引用。 此外，您不应在 index.js 和 App.js 中都包含 BrowserRouter 组件。 一次就够了。

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

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

旁注：在 index.js 的 4+ 版本中默认包含一个名为reportWebVitals的新功能，但它与服务工作者无关。