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?

Solution 1

Please check the following folder:

./your-app/build/web

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

Solution 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/">

Solution 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

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