Flutter Web: Missing main.dart.js and JavaScript files when building with flutter build web, but working fine with flutter run

Question

I am running into an issue with Flutter web in which no JavaScript files are generated when running flutter build web in any project, causing prjects to simply load a blank page.

I am currently on version 1.18.0 beta channel, and this happens with every project, even with the default counter project that Flutter generates with flutter create. . No warnings or errors are thrown, and if I run the web project with flutter run --release -d chrome , everything works as intended.

I have followed the steps described in the Building a web application with Flutter article from the documentation, and I remember I was able to build and host a web project with Flutter half a year ago with no issues, following the same steps.

My Flutter configuration and SDKs seem to be in place. This is what I get if I run flutter doctor -v

[√] Flutter (Channel beta, 1.18.0-11.1.pre, on Microsoft Windows [Versión 10.0.18363.836], locale es-ES)
    • Flutter version 1.18.0-11.1.pre at D:\Programas\Flutter\flutter
    • Framework revision 2738a1148b (4 weeks ago), 2020-05-13 15:24:36 -0700
    • Engine revision ef9215ceb2
    • Dart version 2.9.0 (build 2.9.0-8.2.beta)


[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at C:\Users\diego\AppData\Local\Android\sdk
    • Platform android-28, build-tools 28.0.3
    • Java binary at: D:\Programas\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)
    ! Some Android licenses not accepted.  To resolve this, run: flutter doctor --android-licenses

[√] Chrome - develop for the web
    • Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

[√] Android Studio (version 3.6)
    • Android Studio at D:\Programas\Android Studio
    • Flutter plugin version 46.0.1
    • Dart plugin version 192.8052
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)

[√] Connected device (2 available)
    • Web Server • web-server • web-javascript • Flutter Tools
    • Chrome     • chrome     • web-javascript • Google Chrome 83.0.4103.61

What might be wrong here? Why are no JavaScripts files being generated?

Answer 1

Please check the following folder:

./your-app/build/web

I had the same problem and was checking the wrong folder ( ./your-app/web ).

Answer 2

1. make sure to copy files, from:
   ./your-app/build/web

2. If the error still exists, update the index.html
   Example:
   a. my flutter project at web server: webserver/flutter_project/index.html
   b. open the index.html
   c. update <base href="/"> to <base href="/flutter_project/">

Answer 3

For those who cant open builded version: Go to 'app/build/web' and run a server from there python -m http.server 8000 , or by using the dhttpd package

Docs

Answer 4

The simplest thing that worked for me is updating to <base href="./"> from <base href="/"> . So current path instead of root

Answer 5

In my case (IIS).json files are available in my directory but are not published by the web server. I had to add MIME types to allow them. Same question for.otf files.

Answer 6

In my case, the flutter.js file is not generated when building for web. What I do is run flutter clean then run flutter build web again. You should see the missing js file and make sure to check on build/web not web on the root.