Unknown file extension ".ts" with nodemon --exec ts-node

Question

I created a project on the laptop and set it up. Everything worked fine. Now I'm working on PC, I cloned project and when I start server.ts an error occurs:

megaa@DESKTOP-OIQ46IB MINGW64 /d/Code/Pet-project/server (main)
$ npm run start
> [email protected] start
> nodemon --exec ts-node server.ts
[nodemon] 2.0.22
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: ts,json
[nodemon] starting `ts-node server.ts`
TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for D:\Code\Pet-project\server\server.ts
 at new NodeError (node:internal/errors:405:5)
 at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:99:9)
 at defaultGetFormat (node:internal/modules/esm/get_format:142:36)
 at defaultLoad (node:internal/modules/esm/load:91:20)
 at nextLoad (node:internal/modules/esm/hooks:733:28)
 at load (D:\Code\Pet-project\server\node_modules\ts-node\dist\child\child-loader.js:19:122)
 at nextLoad (node:internal/modules/esm/hooks:733:28)
 at Hooks.load (node:internal/modules/esm/hooks:377:26)
 at MessagePort.handleMessage (node:internal/modules/esm/worker:168:24)
 at [nodejs.internal.kHybridDispatch] (node:internal/event_target:778:20) {
 code: 'ERR_UNKNOWN_FILE_EXTENSION'
}
[nodemon] app crashed - waiting for file changes before starting...

I tried to solve it with removing "type": "module" from package.json - didn't help as well as starting as nodemon --exec ts-node-esm server.ts or nodemon --exec ts-node --esm server.ts. Moreover I have following rows in my tsconfig.json:

"ts-node": {
 "esm": true,
 "experimentalSpecifierResolution": "node"
}

I installed typescript, tsc, ts-node with -g flag as well as nodemon

tsconfig.json:

{
 "compilerOptions": {
 "target": "ES2021",
 "useDefineForClassFields": true,
 "module": "ESNext",
 "lib": [
 "ES2021",
 "DOM",
 "DOM.Iterable"
 ],
 "skipLibCheck": true,
 /* Bundler mode */
 "moduleResolution": "node",
 "allowImportingTsExtensions": true,
 "allowSyntheticDefaultImports": true,
 "resolveJsonModule": true,
 "esModuleInterop": true,
 "isolatedModules": true,
 "noEmit": true,
 /* Linting */
 "strict": true,
 "noUnusedLocals": true,
 "noUnusedParameters": true,
 "noFallthroughCasesInSwitch": true
 },
 "ts-node": {
 "esm": true,
 "experimentalSpecifierResolution": "node"
 }
}

package.json:

{
 "name": "server-side",
 "version": "1.0.0",
 "description": "",
 "main": "./server.ts",
 "scripts": {
 "start": "nodemon --exec ts-node server.ts"
 },
 "author": "",
 "license": "ISC",
 "dependencies": {
 "@types/express": "^4.17.17",
 "chalk": "^5.2.0",
 "cors": "^2.8.5",
 "express": "^4.18.2",
 "mysql": "^2.18.1",
 "ts-node": "^10.9.1",
 "tsc": "^2.0.4"
 },
 "devDependencies": {
 "@types/cors": "^2.8.13",
 "@types/mysql": "^2.15.21",
 "nodemon": "^2.0.22",
 "typescript": "^5.1.6"
 }
}

Let me know if I need to provide any additional information

• k.tten: ts-node is a pain to work with. Just compile it with tsc -w and then nodemon dist/index.js or whatever. Nodemon will watch changes in the dist output and restart the program.
• Dimava: Try tsx (tsx watch server.ts) github.com/esbuild-kit/tsx instead, it's more stable with things like this
• Lvasche: @Dimava it helped. server.ts started. You can write it as an answer and I'll mark it as right

Answer 1

ts-node and ts-node+nodemon are known to be problematic in certain circuimstances (--inspect, cjs/esm interop, some configs), one of which you have encountered.

Try using a more drop-in-and-it-just-works alternative tsx https://github.com/esbuild-kit/tsx
tsx server.ts

It has a builtin watcher, so nodemon is not needed
tsx watch server.ts

---

edit: it's 2024 you should try Bun https://bun.sh/ , which is a node/pnpm alternative with great UX. I now use it for all projects which do not explicitly require node, and even for those I use it as package manager

• SalahAdDin: tsx does not work.
• Tomáš M.: tsx works great! On the other hand, bun has a lot of limitations and is (yet) far from a drop-in alternative to Node.js.