ClojureScript vs Kotlin/JS

ClojureScript is a compiler that turns Clojure code into JavaScript for client and embedded application development wherever JavaScript reaches. It brings Clojure data structures and constructs—including functional programming, macros, destructuring, and polymorphism—into JavaScript environments. Its output is compatible with Google Closure Compiler advanced compilation, which can minify output and eliminate dead code. REPL support enables interactive development and testing in a browser or Node.js; the quick start uses browser output by default and selects Node.js output with a target setting. ClojureScript supports both ClojureScript and JavaScript dependencies, with React demonstrated in the quick start. Listed build tools include shadow-cljs, Figwheel, Leiningen, and lein-cljsbuild. Editor resources cover Cursive, Emacs, VS Code, Light Table, Sublime Text, Vim, and Atom. Documentation includes compiler and REPL options, dependencies, advanced compilation, source maps, and JavaScript module support marked Alpha. The project is open source under the Eclipse Public License 1.0 and lists Linux, macOS, Windows, web, and self-hosted environments.

Kotlin/JS is a Kotlin compiler target that converts Kotlin code, the Kotlin standard library, and compatible dependencies into JavaScript. Projects can target browsers or Node.js, including server-side and serverless applications. It supports ES5, ES2015, and ES2020 output, as well as ESM, CommonJS, UMD, and AMD modules. Projects use the Kotlin Multiplatform Gradle plugin for configuration, bundling, and JavaScript dependencies from npm. Kotlin/JS can share logic between web frontends and JVM backends, or across Android, iOS, and web clients. Kotlin wrappers are available for React and other JavaScript frameworks, including React Redux, React Router, and styled-components. Browser tests can use Karma or an experimental browser testing DSL; Node.js projects use Mocha. The documentation notes that Karma is deprecated and is not expected to receive new features or bug fixes. The Gradle plugin generates JavaScript source maps for builds. Kotlin/JS is open source and free at free, and is listed for Linux, macOS, web, and Windows.