How to Set Up TypeScript in an Existing Next.js Project

Here is a concise answer on how to set up TypeScript in an existing Next.js project:

To add TypeScript to an existing Next.js project, follow these steps:

1. Install the required dependencies:


npm install --save-dev typescript @types/react @types/node

This will install the TypeScript compiler and the necessary type definitions for React and Node.js.

2. Create a `tsconfig.json` file in the root of your project:


touch tsconfig.json

This file will contain the TypeScript configuration for your project.

3. Populate the `tsconfig.json` file with the following configuration:

json
{
  "compilerOptions": {
    "target": "es5",
    "lib": ["dom", "dom.iterable", "esnext"],
    "allowJs": true,
    "skipLibCheck": true,
    "strict": true,
    "forceConsistentCasingInFileNames": true,
    "noEmit": true,
    "esModuleInterop": true,
    "module": "esnext",
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "jsx": "preserve",
    "incremental": true
  },
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"],
  "exclude": ["node_modules"]
}

4. Rename your existing `.js` files to `.ts` or `.tsx` (depending on whether the file contains JSX or not).

5. Restart your development server by running `npm run dev` or `yarn dev`, and your TypeScript code should now be compiled and running alongside your React code.

That's it! You have successfully set up TypeScript in your existing Next.js project. The key steps are installing the required dependencies, creating the `tsconfig.json` file, and renaming your JavaScript files to TypeScript. [2][4]

Citations:
[1] https://www.linode.com/docs/guides/next-js-with-typescript/
[2] https://dev.to/sushmeet/add-typescript-to-an-existing-nextjs-project-in-5-mins-2mik
[3] https://www.geeksforgeeks.org/how-to-add-typescript-in-next-js/
[4] https://blog.savetchuk.com/how-to-add-typescript-to-existing-nextjs-project
[5] https://nextjs.org/docs/getting-started/installation

How do I set up TypeScript in an existing Next.js project