[Blazor] .NET 9 generated JS uses high version syntax leading to compatibility issues

[capdiem]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

The blazor.*.js files generated by .NET 9 utilize the static initialization block feature introduced in ES13. This usage causes compatibility issues on lower-end devices and older browsers.
You can find instances of this issue by searching for static{ in the generated files.

static{this.nextEventDelegatorId=0}

related issue: dotnet/maui#24278 dotnet/maui#25862

Expected Behavior

Regenerate using ES6 as the target, just like before.

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

net9.0

Anything else?

No response

[danroth27]

Our official support policy is that we only support the latest browser versions. Since most users automatically update their browser, we find this isn't generally an issue. When setting up test devices, we recommend similarly updating the browser/webview to emulate this common user behavior.

[capdiem]

@danroth27 While it's true that most users automatically update their browsers, not all users are accustomed to doing so. Setting the tsconfig target to a version as high as ES2022 can lead to compatibility issues, especially considering that .NET 8 targets ES2019.

For a framework with such a large user base, backward compatibility is crucial. Many popular JavaScript libraries set their minimum support to ES2015, and I believe that for Blazor, targeting ES2019 would be a more reasonable approach. This change would help prevent any breaking updates when upgrading to .NET 9.

Thank you for your reply!