Converting a Next.js project from TypeScript to plain JavaScript

Converting a Next.js project from TypeScript to plain JavaScript involves several steps, primarily changing file extensions and removing TypeScript-specific syntax. Here’s a step-by-step guide to help you with this conversion:

1. Rename File Extensions: Change all .ts and .tsx files to .js and .jsx respectively. This can be done manually or via a script.

2. Remove TypeScript Syntax: TypeScript introduces type annotations and interfaces which need to be removed. You will need to:

   • Remove all type annotations.

   • Remove all interface and type definitions.

   • Remove any imports from types files.

3. Update Imports: Update your imports to point to the new JavaScript files instead of TypeScript files.

4. Remove TypeScript Configuration: Delete tsconfig.json file as it’s no longer needed.

5. Update Dependencies: Remove TypeScript and related type packages from your package.json. For example, you can remove:

   "@types/node": "version",
   "@types/react": "version",
   "typescript": "version"

6. Update ESLint and Prettier Configurations: If you have TypeScript-specific configurations for ESLint or Prettier, remove or update them accordingly.

Here's an example of what you might need to do in detail:

Step-by-Step Conversion Example

Step 1: Rename File Extensions

Rename files:

• index.tsx -> index.jsx

• app.ts -> app.js

• etc.

Step 2: Remove TypeScript Syntax

Before (TypeScript):

// pages/index.tsx
import { NextPage } from 'next';
import { AppProps } from 'next/app';

const Home: NextPage = ({ title }: { title: string }) => {
  return <h1>{title}</h1>;
};

export default Home;

After (JavaScript):

// pages/index.jsx
import React from 'react';

const Home = ({ title }) => {
  return <h1>{title}</h1>;
};

export default Home;

Step 3: Update Imports

Make sure all your imports now refer to .js or .jsx files.

Step 4: Remove TypeScript Configuration

Delete tsconfig.json.

Step 5: Update Dependencies

Remove TypeScript-related dependencies:

npm uninstall typescript @types/node @types/react

After completing these steps, your Next.js project should be converted from TypeScript to plain JavaScript. Make sure to thoroughly test your application to ensure everything is functioning correctly after the conversion.