Babel vs Scala.js

Babel is a JavaScript compiler that converts modern syntax into code compatible with current and older browsers or other environments. Its transformation pipeline is built from plugins, which users can combine into presets or write themselves. Babel provides transformers for the latest JavaScript and a React preset for JSX. It can also add features through third-party polyfills such as core-js, run codemods, and remove Flow or TypeScript type annotations; it does not check types. Source maps support debugging compiled output. The command-line interface can compile files or directories, watch for changes, and generate source maps. Installation documentation covers npm, Yarn, pnpm, and Bun. A standalone build can run in browsers and other non-Node.js environments, including on scripts marked text/babel or text/jsx, but the documentation recommends ahead-of-time transpilation with a Node.js build system for production. Babel is free, MIT-licensed, community-funded, and maintained by volunteers. The project directs support questions to GitHub Discussions, Slack, Stack Overflow, or Bluesky.

Scala.js is a Scala-to-JavaScript compiler for building applications that run in browsers, Node.js, and serverless environments. The project also states that WebAssembly support is stable. Scala's strong typing can catch mistakes such as mixing strings and numbers or using misspelled method names, while editor support can flag type errors and show inline details about methods, arguments, return types, and documentation. The project describes incremental compilation with a 1–2 second turnaround; generated JavaScript for a full application starts at 45 kB gzipped. Scala.js can use JavaScript libraries and APIs through statically or dynamically typed access. Listed library integrations include React, Angular, Vue, Three.js, and Chart.js. Build tool options include sbt, scala-cli, Mill, and Gradle with a Scala.js plugin. Tutorials list Scala development tools and Node.js as prerequisites and recommend VS Code with Metals. Scala.js is free and distributed under the Apache License 2.0. Documentation points users to community support through Discord and Stack Overflow. The 1.22.0 release is not entirely backward source compatible with 1.21.x.