[React.js]尝试导入错误：'./registerServiceWorker' 不包含默认导出（导入为'registerServiceWorker'）

Posted 2023-03-07

【中文标题】[React.js]尝试导入错误：\'./registerServiceWorker\' 不包含默认导出（导入为\'registerServiceWorker\'）

【英文标题】：[React.js]Attempted import error: './registerServiceWorker' does not contain a default export (imported as 'registerServiceWorker')[React.js]尝试导入错误：'./registerServiceWorker' 不包含默认导出（导入为'registerServiceWorker'）

【发布时间】：2020-05-18 08:45:25

【问题描述】：

我正在尝试创建一个获取 pokemon API 的反应应用程序，但我遇到了以下问题，提示尝试导入错误：'./registerServiceWorker' 不包含默认导出（导入为'registerServiceWorker'）。但我的 App.js 文件中确实有一个export default App;，这是我的以下内容，不太确定是什么问题，将不胜感激。

App.js

import React,  Component  from 'react';
import './styles/App.css';


class App extends Component 
  render() 
    return (
      <div className="App">
        hellohello
      </div>
    );
  



export default App;

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

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

const isLocalhost = Boolean(
  window.location.hostname === 'localhost' ||
    // [::1] is the IPv6 localhost address.
    window.location.hostname === '[::1]' ||
    // 127.0.0.0/8 are 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) 

    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
    if (publicUrl.origin !== window.location.origin) 

      return;
    

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

      if (isLocalhost) 
        checkValidServiceWorker(swUrl, config);


        navigator.serviceWorker.ready.then(() => 
          console.log(
            'This web app is being served cache-first by a service ' +
              'worker.'
          );
        );
       else 
        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) 

              console.log(
                'New content is available and will be used when all ' +
                  'tabs for this page are closed.'
              );


              if (config && config.onUpdate) 
                config.onUpdate(registration);
              
             else 

              console.log('Content is cached for offline use.');


              if (config && config.onSuccess) 
                config.onSuccess(registration);
              
            
          
        ;
      ;
    )
    .catch(error => 
      console.error('Error during service worker registration:', error);
    );


function checkValidServiceWorker(swUrl, config) 
  fetch(swUrl, 
    headers:  'Service-Worker': 'script' 
  )
    .then(response => 
      const contentType = response.headers.get('content-type');
      if (
        response.status === 404 ||
        (contentType != null && contentType.indexOf('javascript') === -1)
      ) 
        navigator.serviceWorker.ready.then(registration => 
          registration.unregister().then(() => 
            window.location.reload();
          );
        );
       else 
        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();
    );
  

【问题讨论】：

也粘贴此文件 (registerServiceWorker.js) 代码。

@GangadharGandi 是的，我已经粘贴了，谢谢。

【参考方案1】：

您的模块没有默认导出。它有一个命名导出register。

您可以使用别名registerServiceWorker 导入它：

import  register as registerServiceWorker  from './registerServiceWorker';