Scala.js vs Transcrypt

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.

Transcrypt compiles Python source code into JavaScript for browser applications. It converts a substantial subset of Python into JavaScript 6, with optional minification, and supports features including multiple inheritance, async/await, comprehensions, and modules. Developers can call JavaScript functions from Python and use browser DOM functions and JavaScript libraries. The distribution includes optional static type validation and consistency checks, plus multilevel source maps for tracing generated JavaScript back to the original Python. Transcrypt can also compile Python server code for Node.js and use Node libraries with require(). The project recommends installing it as a Python package with pip and documents testing on Windows, Linux, and OSX. Its focus is browser development and JavaScript libraries rather than desktop Python libraries. Because code is precompiled, Python exec and eval are unsupported, although JavaScript eval is supported. C and C++ libraries are not directly supported for browser use without special measures such as compiling them to asm.js. Transcrypt is free and open source under Apache 2.0.