Default Project not working on Windows 11

[yurtemre7]

Hey, thank you for your time.

I tried to setup a project but sadly encountered an issue.

The following setup I have is the exact setup described on the home page.
I'm using Windows 11.

Dart:

# extraced from `flutter doctor -v`
Dart version 3.10.7

Node/NPM:

> node -v
v22.14.0
> npm -v
11.7.0

lib/server.dart

import 'package:dart_node_express/dart_node_express.dart';

void main() {
  final app = express();
  app.get('/', handler((req, res) => res.send('Hello, Dart!')));
  app.listen(3000);
}

First building the project works fine:

> dart compile js lib/server.dart -o build/server.js
Compiled 10,273,865 input bytes (5,277,075 characters source) to 129,091 characters JavaScript in 0.36 seconds

But then running it:

> node build/server.js
C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:1360
      throw A.initializeExceptionWrapper(A._errorForAsCheck(object, testRti), new Error());
      ^

TypeError: null: type 'JSNull' is not a subtype of type 'JavaScriptFunction'
    at Rti._generalAsCheckImplementation [as _as] (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:1360:79)
    at Rti._installSpecializedAsCheck (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:1295:22)
    at Object.express (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:2546:17)
    at main (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:2582:19)
    at C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:3374:7
    at C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:3351:7
    at dartProgram (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:3368:5)
    at Object.<anonymous> (C:\Users\emrey\Programming\dartprojs\dartkanji\build\server.js:3377:3)
    at Module._compile (node:internal/modules/cjs/loader:1554:14)
    at Object..js (node:internal/modules/cjs/loader:1706:10) {
  dartException: _TypeError {
    '__rti$_message': "TypeError: null: type 'JSNull' is not a subtype of type 'JavaScriptFunction'"
  }
}

Node.js v22.14.0

Hope you have a great day and thanks for making this project.

[ajayi-joseph]

Hey @yurtemre7
That's a really cryptic error message. Looking at your code and the error, it seems like the issue is that Express isn't installed via npm.

The thing with dart_node_express is that it's actually a wrapper around the real Express.js library. So you need both the Dart package (which you have) and the npm package. When your code calls express(), it's trying to load the actual Express.js module, but if it's not installed, you get this confusing type error.

Try running this in your project directory:

npm install express

You might need to create a package.json first if you don't have one then compile and run again

[yurtemre7]

hey, i did setup a node project too and added express via npm. Sadly still encountering this issue on my Windows machine.

[ajayi-joseph]

Hey @yurtemre7 I suspect Node.js can't find the Express module.

Since you mentioned you already installed Express, try running from the build directory instead:

cd build
node server.js

If that doesn't work, the issue is likely that your package.json and node_modules are in the wrong location relative to where you're running the compiled JavaScript.

Can you share your folder structure? Just want to see where your package.json, node_modules, and build/server.js files are located.

[yurtemre7]

Sure here is my folder structure:

> ls


    Directory: C:\Users\emrey\Programming\dartprojs\dartkanji


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----        1/20/2026   8:02 PM                  .dart_tool
d-----        1/20/2026   8:05 PM                  build
d-----        1/20/2026   8:03 PM                  example
d-----        1/20/2026   8:04 PM                  lib
d-----        1/20/2026   8:06 PM                  node_modules
d-----        1/20/2026   8:04 PM                  test
-a----        1/20/2026   8:02 PM            221   .gitignore
-a----        1/20/2026   8:02 PM           1038 󰉢  analysis_options.yaml
-a----        1/20/2026   8:02 PM             29   CHANGELOG.md
-a----        1/21/2026   1:43 PM          28929   package-lock.json
-a----        1/20/2026   8:12 PM            581   package.json
-a----        1/20/2026   8:03 PM          12138   pubspec.lock
-a----        1/20/2026   8:13 PM            338 󰉢  pubspec.yaml
-a----        1/20/2026   8:02 PM           1264 󰪷  README.md

Inside lib I have my server.dart file with the main function.

Inside build there are the , server.js.deps and server.js.map files.