Uncaught Error: Cannot find module './App' at webpackMissingModule

I'm receiving the error Uncaught Error: Module not found: Can't resolve ./App' and ./store in client/src. in the console of the local environment when I run npm start from the client directory.

The screen renders 2 errors.

• ERROR in ./src/index.tsx 7:0-24 Module not found: Error: Can't resolve './App.tsx' in '/client/src'
• ERROR in ./src/index.tsx 7:0-24 Module not found: Error: Can't resolve './store.ts' in '/client/src'

However, when I import the client directory of my project into a CodeSandbox, it is working.

client/src/index

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import { Provider } from 'react-redux';
import { PersistGate } from 'redux-persist/integration/react';
import persistStore from 'redux-persist/es/persistStore';
import setupStore from './store';

const store = setupStore();
const persistor = persistStore(store);

ReactDOM.render(
    <Provider store={store}>
        <PersistGate loading={null} persistor={persistor}>
            <App />
        </PersistGate>
    </Provider>,
    document.getElementById('root'),
);

Solution Attempts:

• delete node_modules and package-lock.json, then npm install
• npm cache clean --force and npm cache clear --force
• assured the dependencies and packages installed in my local environment are the same in CodeSandbox.
• Made sure that the App component and the store module actually exist in the src/ directory.
• Checked that the file name for both App and store is spelled correctly and that the file extension is correct as well (e.g., .tsx for React components).
• assured file paths are correct
• using Chrome on both local and CodeSandbox

What's going on?

It looks like you started with a JavaScript project generated by Create React App and then you tried to migrate the project to TypeScript.

When you make this migration, the Create React App scripts are supposed to automatically generate a tsconfig.json file as soon as you rename any of your *.js files to *.ts. However, it seems that currently there is an issue and the tsconfig.json file is NOT automatically generated - this is the root cause for the error you see.

The workaround is simple: generate the tsconfig.json file manually. You can see an example file generated by Create React App when it actually works here: https://github.com/facebook/create-react-app/issues/10951#issuecomment-839711690.