Announcing Scala.js 1.19.0

Announce
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Hello everyone,

We are pleased to announce the release of Scala.js 1.19.0!

This release comes with significant performance improvements to the WebAssembly backend. For codebase where performance is dominated by computations (rather than JS interop), you can now expect the Wasm output to be faster than the JS output.

Moreover, as of this writing, the latest versions of Firefox (since v131) and Safari (since v18.4) support all the WebAssembly features required to run Scala.js-on-Wasm. Chrome still requires a flag to enable exception handling.

If you haven’t tried the WebAssembly target yet, now is a good time to do so!

Other highlights:

  • Native support for JavaScript async/await, through js.async { ... } and js.await(...).
  • Small code size improvements for the JavaScript target when using SAM lambdas.
  • For Wasm only: support for the JavaScript Promise Integration feature (JSPI).

Read the announcement on the Web for more details:

Enjoy!
the Scala.js team

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As I mentioned elsewhere on social media, the JSPI support is IMO a game changer. As long as you enter a js.async { ... } block, you can synchronous await a JS Promise anywhere with js.await(p) ! That has never been possible on the JS platform. I can’t wait to see what libraries will be built on top of this new superpower.

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