I got tired of messy TypeScript migrations in Node.js, so I built fast-ts-integrator

Source: Dev.to

Adding TypeScript to an existing Node.js project

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.

What it is

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.

Why I built it

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.

Quick start

npx fast-ts-integrator

or

npx fast-ts

Example flow

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.

Links

• npm: fast-ts-integrator on npm
• GitHub: fast-ts-integrator repository

Still improving

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.