Adding TypeScript to an existing Node.js project sounds simple until it isn’t. A few files in, things usually start drifting: tsconfig.json stops matching the actual runtime CommonJS and ESM start fighting each other mixed .js and .ts files make the project harder to reason about test and lint setup adds even more friction I kept running into that same wall, so I built a small CLI to make the setup predictable. fast-ts-integrator is a CLI that helps add TypeScript to a new or existing Node.js project with an interactive setup. It lets you choose: ES Modules or CommonJS tsx or ts-node Biome or ESLint + Prettier Vitest or Jest Then it installs what is needed, generates the config, and adds the scripts so you can actually start working instead of fighting setup. Most of the pain was never “TypeScript itself”. It was the setup around it: choosing the right module strategy keeping runtime behavior consistent avoiding broken imports after migration wiring linting and testing without turning the project into config soup I wanted something practical that works for real Node.js projects, not just empty demos. npx fast-ts-integrator or npx fast-ts The CLI walks through a few choices: module system execution engine linter/formatter test framework After that, it scaffolds the setup and updates package.json for you. npm: npm package Github Repo This is an early release, and I’m actively improving it. Real feedback would help a lot, especially from people who have dealt with: gradual JS to TS migration CommonJS to ESM headaches existing Express or Node backends lint/test setup that tends to break during migration If you try it, I’d genuinely like to know what feels smooth and what feels annoying.