TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" in Node v21.5.0

[cibilex]

First of all ,I already looked at https://github.com/TypeStrong/ts-node/issues/1997 and most of other websites to solve the problem but I couldn't.This error is throwed when I try to use in Node v21.5.0.I realized that The problem is node version,when I updated Node version to v19.0.0 it works.Could you please update ts-node to work in new Node versions.

Best regards.

[AaronNGray]

Getting same issue, but I have a working version that I solved this issue on, and now a new project on which it does not. It is something else and I cannot remember what it is. Will report back once I have debugged the issue.

[AaronNGray]

Heres a working example with node v21.5.0, typescript v5.3.3, ts-node v10.9.2 :- https://github.com/AaronNGray/ts-node-example

NOTE: I have just found this does not seem to support imports !!!

[AaronNGray]

First of all ,I already looked at #1997 and most of other websites to solve the problem but I couldn't.This error is throwed when I try to use in Node v21.5.0.I realized that The problem is node version,when I updated Node version to v19.0.0 it works.Could you please update ts-node to work in new Node versions.

Could you please provide a minimal example of what does not work and then we can try to figure out why !

[peschee]

Heres a working example with node v21.5.0, typescript v5.3.3, ts-node v10.9.2 :- https://github.com/AaronNGray/ts-node-example

This is not an ESM package. Try setting type to module in your package.json.

[AaronNGray]

Heres a working example with node v21.5.0, typescript v5.3.3, ts-node v10.9.2 :- https://github.com/AaronNGray/ts-node-example

This is not an ESM package. Try setting type to module in your package.json.

AFAICS I am not sure ts-node supports ESM. Could you provide the example that works on node v19.0.0, but not v21.5.0. Or is it as simple as setting "type":"module" ? As in :- https://github.com/AaronNGray/ts-node-example/tree/ts-node-esm-module

on v21.5.0 resulting in :-

C:\Users\Nathaniel\test\Node.js\ts-node-example>npm start

> [email protected] start
> ts-node src/index.ts

TypeError: Unknown file extension ".ts" for C:\Users\Nathaniel\test\Node.js\ts-node-example\src\index.ts
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:160:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:203:36)
    at defaultLoad (node:internal/modules/esm/load:143:22)
    at async ModuleLoader.load (node:internal/modules/esm/loader:409:7)
    at async ModuleLoader.moduleProvider (node:internal/modules/esm/loader:291:45)
    at async link (node:internal/modules/esm/module_job:76:21) {
  code: 'ERR_UNKNOWN_FILE_EXTENSION'
}

[AaronNGray]

Adding :-

"start:node": "node --loader ts-node/esm src/index.ts"

and tsconfig.json :-

"module": "esnext"

We have :-

https://github.com/AaronNGray/ts-node-example/tree/ts-node-esm-loader

which gives :-

C:\Users\Nathaniel\test\Node.js\ts-node-example>npm run start:node

> [email protected] start:node
> node --loader ts-node/esm src/index.ts

(node:18508) ExperimentalWarning: `--experimental-loader` may be removed in the future; instead use `register()`:
--import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));'
(Use `node --trace-warnings ...` to show where the warning was created)
ts-node

NOTE: I have just found this does not seem to support imports !!!

[cibilex]

First of all ,I already looked at #1997 and most of other websites to solve the problem but I couldn't.This error is throwed when I try to use in Node v21.5.0.I realized that The problem is node version,when I updated Node version to v19.0.0 it works.Could you please update ts-node to work in new Node versions.

Could you please provide a minimal example of what does not work and then we can try to figure out why !

I've modified the project a bit and created new repository.link: https://github.com/cibilex/ts-node-err

This project doesn't work in node v21.5.0 while works In node v16.20.2 for me.

[AaronNGray]

First of all ,I already looked at #1997 and most of other websites to solve the problem but I couldn't.This error is throwed when I try to use in Node v21.5.0.I realized that The problem is node version,when I updated Node version to v19.0.0 it works.Could you please update ts-node to work in new Node versions.

Could you please provide a minimal example of what does not work and then we can try to figure out why !

I've modified the project a bit and created new repository.link: https://github.com/cibilex/ts-node-err

This project doesn't work in node v21.5.0 while works In node v16.20.2 for me.

You modified start to : -"start": "ts-node-esm src/index.ts"

The version I posted last works AFAICT without proper testing, but I did do an import

Note: --loader maybe deprecated.

https://github.com/AaronNGray/ts-node-example/tree/ts-node-esm-loader

NOTE: I have just found this does not seem to support imports !!!

[AaronNGray]

@cibilex - Theres a pull request waiting :- https://github.com/TypeStrong/ts-node/pull/2073

[cibilex]

@cibilex - Theres a pull request waiting :- #2073

Thank you a lot,It works now splendid :)

[AaronNGray]

@cibilex - Did you manage to add the two commits to a ts-node fork or did you just patch the diff's ? If you used git I would love to know how ! On the other front I seem to remember GitHub giving diffs but it does not seem to have downloads for them anymore. Or did you just use a reference to the repo in package.json dependencies ?

[cj-christoph-gysin]

@cibilex - Did you manage to add the two commits to a ts-node fork or did you just patch the diff's ? If you used git I would love to know how !

$ git fetch https://github.com/TypeStrong/ts-node refs/pull/2073/head
$ git checkout -b pr-2073 FETCH_HEAD

On the other front I seem to remember GitHub giving diffs but it does not seem to have downloads for them anymore.

You can just add .diff or .patch to any github url for a commit or PR, e.g.: https://github.com/TypeStrong/ts-node/pull/2073.diff

[AaronNGray]

@cibilex - Wow great thanks, think I was over complicating things :)

[MickL]

Guys no need for ts-node, just use Deno or Bun:

deno run main.ts
bun run main.ts

[russell-miburn]

Is there an update on the progress of this bug?

[francip]

To summarize: Looks like this has been there for a while. Adding "type"="module" to package.json breaks ts-node --esm for any node version above v16.

The workarounds I've found so far:

• remove "type="module"
• downgrade to node v16
• use node --loader ts-node/esm instead of ts-node --esm (comes with a warning)
• use node --import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));' instead of ts-node --esm (to avoid the warning)
• use tsx instead of ts-node

If you are using webpack in your project, this also breaks using Typescript config files. The only workaround for this are:

• switch back to JS config file
• remove "type="module"
• downgrade to node v16

[zq0904]

First of all ,I already looked at #1997 and most of other websites to solve the problem but I couldn't.This error is throwed when I try to use in Node v21.5.0.I realized that The problem is node version,when I updated Node version to v19.0.0 it works.Could you please update ts-node to work in new Node versions.

Best regards.

Odd-numbered versions of node are typically beta versions and should not be supported

[russell-miburn]

I realised that the issue that I had was not with the version of node or ts-node but I was importing a typescript dependancy incorrectly from a library. removing the dependency i was importing and importing the .js from the library rather that a typescript file fixed this issues.

[francip]

Update: The node version where ts-node with package.json "type"="module" breaks is v18.19.0

Simple repro - francip/ts-node-test

[djomajeff]

I use node v20.10.0.

In Package.json apply this configuration:

• Here is my start script : nodemon --exec node --no-warnings=ExperimentalWarning --loader ts-node/esm src/index.ts
• Add "type": "module",
• In dependencies add the matching @types dependencies in devDependencies if exists on npm for type completion: "devDependencies": { "@types/node": "^20.11.26", "@types/jsonwebtoken": "^9.0.6", "@types/express": "^4.17.21", "nodemon": "^3.1.0", "ts-node": "^10.9.2", "typescript": "^5.4.2" }, "dependencies": { "cors": "^2.8.5", "express": "^4.18.3", "jsonwebtoken": "^9.0.2" }

In tsconfig.json apply the following:

• "module": "ESNext", "target": "ESNext"
• "esModuleInterop": true, "moduleResolution": "Node"
• At the same level of compiler option add "ts-node": { "esm": true, }

Hope It will work !!

[AaronNGray]

@djomajeff - building a repo following your instructions I am getting :- https://github.com/AaronNGray/ts-node-esm-test/issues/1

I added you to the repo.

[AaronNGray]

@cibilex https://github.com/AaronNGray/ts-node-esm-test works fine now ! I have added a node --test example too.

[sleep-written]

One of the reasons for the failures with ts-node in ESM projects is linked to the file extensions in import statements. To understand the problem, let's envision this directory structure:

.
├── node_modules
├── src
│   ├── sum.ts
│   └── index.ts
├── package.json
├── package-lock.json
└── tsconfig.json

In ESM, you must use the .js extension in your imports. For example, check ./src/index.ts:

import { sum } from './sum.js';  // ...but in reality, the actual file ends in ".ts"

const r = sum(55, 66);
console.log('value:', r);

Thus, when the original ts-node loader receives that import ./sum.js, it tries to resolve it as a ".js" file. But in reality, that file does not exist, and the available file ends with ".ts". To solve the problem, you have several options:

• Rename all your imports from ".js" to ".ts":

  This solves the problem with ts-node, but when you transpile your project, you will need to transform your imports back to ".js".

• Modify the ts-node loader:

  You must intercept all import statements and change the extension from ".js" to ".ts" only when attempting to execute ".ts" files.

I have created a module called @bleed-believer/path-alias (with ts-node as a dependency). Initially created to resolve path aliases, it now also solves this issue. To execute TypeScript files in ESM directly in Node 20 and above:

# Install the library:
npm i --save @bleed-believer/path-alias

# Execute your code using the command line:
npx bb-path-alias ./src/index.ts

# ...or if you need to execute using the node executable:
node --import @bleed-believer/path-alias ./src/index.ts

[francip]

@sleep-written Both ECMA 2025 and ECMA 2020 do not specify explicit extension, and the only import examples I found in both ( ECMA 2025, ECMA 2020 ) do not include any extension. But that's neither here, nor there...

If you look at my example, you will see nowhere do I use import statement, and the failure happens with a single file project. This is a basic scenario where ts-node should work without extra intermediaries.

Though, for folks who are just looking for a quick workaround, your solution might be good.

[sleep-written]

Hi @francip, your example is relevant for Node.js versions 18 and earlier. However, when using Node.js version 20 or above with the command:

node --loader ts-node/esm ./src/index.ts

...you might encounter the following output:

(node:2036531) ExperimentalWarning: --experimental-loader may be removed in the future; instead use register(): --import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));' (Use node --trace-warnings ... to show where the warning was created)

To address this, consider creating a ./ts-node.register.mjs file with:

import { pathToFileURL } from "node:url";
import { register } from "node:module";

register("ts-node/esm", pathToFileURL("./"));

And then launch your application with:

node --import ./ts-node.register.mjs ./src/index.ts

This approach should seamlessly solve the issue, unless your project uses relative imports. According to the Node.js import specifiers:

Relative specifiers like './startup.js' or '../config.mjs'. They refer to a path relative to the location of the importing file. The file extension is always necessary for these.

More details of this problem are explained in this comment. If executing your file with the ./ts-node.register.mjs preloaded results in errors due to relative imports, consider using my module register at @bleed-believer/path-alias. This or building a custom ts-node module register, with the required logic for address relative/absolute imports, could provide a solution too.

[francip]

My example is relevant for node v18.19 and above, where ts-node --esm index.ts command is broken and returns ERR_UNKNOWN_FILE_EXTENSION. (the original problem this issue tracks)

The node --loader ts-node/esm index.ts syntax being deprecated is a separate issue, and the simplest workaround for that is using node --import 'data:text/javascript,import { register } from "node:module"; import { pathToFileURL } from "node:url"; register("ts-node/esm", pathToFileURL("./"));' index.ts or your library which essentially does very similar thing. And yes, they both will successfully run index.ts, which is why I listed them as potential workarounds.

However, this workaround does not help people who want to use ESM, webpack, and TS for their webpack config, as webpack internally calls ts-node, thus hitting the same issue.

[sleep-written]

@francip i made a fork of your example, adding a function:

.
├── README.md
├── another-function.ts    # this file.
├── index.ts
├── package-lock.json
├── package.json
└── tsconfig.json

...and importing that funcion using the ESM syntax according to the node.js documentation:

import { anotherFunction } from './another-function.js';     // Here

export function hello(who: string = "world"): string {
    return `Hello ${who}! `;
}

console.log(hello("ts-node"));
anotherFunction();

The result of execute npm run start is the following:

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /home/sleep-written/projects/node.js/ts-node-test/index.ts at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:160:9) at defaultGetFormat (node:internal/modules/esm/get_format:203:36) at defaultLoad (node:internal/modules/esm/load:143:22) at async nextLoad (node:internal/modules/esm/hooks:866:22) at async nextLoad (node:internal/modules/esm/hooks:866:22) at async Hooks.load (node:internal/modules/esm/hooks:449:20) at async handleMessage (node:internal/modules/esm/worker:196:18) { code: 'ERR_UNKNOWN_FILE_EXTENSION' }

However, with npm run start:success works as you suggest. But when I had to update my library to be compatible with node 20, I had to write my own loader to resolve the path aliases. Since I had to write the loader myself, I ran into exactly that problem with the extensions.

In conclusion, as you say, if you only want to make ts-node able to execute typescript code, you would simply have to implement a module that is preloaded with the --import flag.

[darcyrush]

To address this, consider creating a ./ts-node.register.mjs file with:

import { pathToFileURL } from "node:url";
import { register } from "node:module";

register("ts-node/esm", pathToFileURL("./"));

Thank you all for this, I am able to use ts-node and ESM with my toolset.

I look forward to https://github.com/TypeStrong/ts-node/pull/2073 being merged

[AaronNGray]

@darcyrush - How do you apply this on the command line ?

[darcyrush]

@AaronNGray My use case is very basic;

TS_NODE_PROJECT=./test/tsconfig.json node --import ./ts-node.register.mjs --test-reporter spec --test 'test/**/*.test.ts'

I use that with Node 21 and above for the native test suite functionality. Test suite execution performance is very slow however. I'm not sure if that's a nodejs issue or a ts-node issue.

I used tsx briefly which had much better performance, but I came across a bunch of some edge cases and incompatibility issues with other libraries which is why I came back to ts-node.