This example shows how to integrate the TypeScript type system into Next.js. Since TypeScript is supported out of the box with Next.js, all we have to do is to install TypeScript.
npm install --save-dev typescript
To enable TypeScript's features, we install the type declarations for React and Node.
npm install --save-dev @types/react @types/react-dom @types/node
When we run next dev the next time, Next.js will start looking for any .ts or .tsx files in our project and builds it. It even automatically creates a tsconfig.json file for our project with the recommended settings.
Next.js has built-in TypeScript declarations, so we'll get autocompletion for Next.js' modules straight away.
A type-check script is also added to package.json, which runs TypeScript's tsc CLI in noEmit mode to run type-checking separately. You can then include this, for example, in your test scripts.