@fynjs/ts-resolve

Run this repo's TypeScript on plain node, with no transpiler.

Node already strips TypeScript types natively. What it deliberately does not do is rewrite import specifiers, so ./foo.js will not find foo.ts and extensionless ./foo will not resolve at all. That gap is the only reason a runner like tsx was needed here.

This package fills exactly that gap: a resolve hook, and nothing else. Once it hands back a .ts URL, node's own type stripping compiles it. There is no load hook, no transpiler dependency, no native binary, and no postinstall.

Usage

node --import @fynjs/ts-resolve/register src/entry.ts

Or programmatically:

import { install } from "@fynjs/ts-resolve";
install();

What it maps

| specifier | resolves to | | --- | --- | | ./foo.js | ./foo.ts, ./foo.tsx | | ./foo.mjs | ./foo.mts, ./foo.ts | | ./foo.cjs | ./foo.cts, ./foo.ts | | ./foo | ./foo.ts, .tsx, .mts, .cts, then ./foo/index.* |

A real .js file always wins - an existing file is never shadowed by a .ts of the same name. node_modules and the fynpo store are never remapped.

Why no source maps

Node replaces type annotations with whitespace rather than re-printing the file, so line and column numbers survive stripping untouched. Stack traces point at the original .ts with no source map involved.

Limits

Node's stripping erases types; it never converts module syntax. A .ts file using import/export inside a package that is not "type": "module" will fail with Unexpected token 'export'. The fix belongs in that package's package.json, not here.

JSX is not supported - node cannot strip it. This repo has no .tsx sources.

Requirements

Node >= 22.18, for two reasons: the synchronous in-thread module.registerHooks API (node 22.15), and node's native TypeScript type-stripping being on by default (node 22.18) so that --import @fynjs/ts-resolve/register.ts can load at all. Below 22.18 the hook's own entry point cannot be read.

How require() is covered

install() registers the resolve hook and wraps Module._resolveFilename.

The wrap is not redundant. A CommonJS file run as the entry point is loaded through the ESM loader's CJS translator, and below node 26.2 the require that translator hands it goes straight to Module._resolveFilename without consulting registerHooks - so the hook never sees those specifiers and require("./lib.js") fails with MODULE_NOT_FOUND. From 26.2 the hook covers that path too and the wrap simply agrees with it.

Resolution is all that was ever missing: node's CJS loader already strips types from a .ts file it is handed, on every version this package supports.