How to run TypeScript CLI tasks in a Next.js app

README.md

Assuming you've got a Next.js app that's already using TypeScript to render pages/components or handle API routes, but you also want to be able to run ad hoc build tasks written in TypeScript (perhaps pulling in type files used by the app)...

1. Add these deps: npm install -D @babel/core @babel/node
2. Make sure your Next app has an explicit .babelrc file:

// Default Next.js .babelrc (it's OK if you also have extra stuff in it)
{
  "presets": ["next/babel"],
  "plugins": []
}

Now you can run .ts files like this:

babel-node -x .ts myTask.ts

(Put that in a package.json script and run it with npm run taskname, or prefix babel-node with ./node_modules/.bin/ to run it directly.)

It is OK for your task to fail type-checking, it will still run.