Error: A value of type 'JSString' can't be assigned to a variable of type 'String'

[ashitaprasad]

Describe the bug
Unable to build Flutter app for web

Launching lib/main.dart on Chrome in debug mode...
../../../.pub-cache/hosted/pub.dev/printing-5.13.4/lib/printing_web.dart:218:16: Error: 
A value of type 'JSString' can't be assigned to a variable of type 'String'.
              .toJS;
               ^
Failed to compile application.

Expected behavior
It should build for web

Flutter Doctor

[✓] Flutter (Channel stable, 3.24.3, on macOS 14.6.1 23G93 darwin-arm64, locale en-IN)
    • Flutter version 3.24.3 on channel stable at /Users/ap/Documents/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 2663184aa7 (3 months ago), 2024-09-11 16:27:48 -0500
    • Engine revision 36335019a8
    • Dart version 3.5.3
    • DevTools version 2.37.3

[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
    • Android SDK at /Users/ap/Library/Android/sdk
    • Platform android-35, build-tools 35.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.4)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 15F31d
    • CocoaPods version 1.15.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)

[✓] IntelliJ IDEA Community Edition (version 2023.1.2)
    • IntelliJ at /Applications/IntelliJ IDEA CE.app
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart

[✓] VS Code (version 1.95.3)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.102.0

[✓] Connected device (4 available)
    • Ashita’s iPhone (mobile)        • 00008030-000951A01A02402E • ios            • iOS 18.1 22B83
    • macOS (desktop)                 • macos                     • darwin-arm64   • macOS 14.6.1 23G93
      darwin-arm64
    • Mac Designed for iPad (desktop) • mac-designed-for-ipad     • darwin         • macOS 14.6.1 23G93
      darwin-arm64
    • Chrome (web)                    • chrome                    • web-javascript • Google Chrome
      131.0.6778.140

[✓] Network resources
    • All expected network resources are available.

• No issues found!

Desktop (please complete the following information):

• iOS
• Android
• Browser
• Windows
• Linux

[ashitaprasad]

Upon further investigation I found the fix:

Changing

      script.innerHTML =
          '''function ${_frameId}_print(){var f=document.getElementById('$_frameId');f.focus();f.contentWindow.print();}'''
              .toJS;

to

      script.innerHTML =
          '''function ${_frameId}_print(){var f=document.getElementById('$_frameId');f.focus();f.contentWindow.print();}''';

JSString conversion using .toJS is no longer required.

There is already an open PR #1739 which fixes the issue.