ClojureScript

ClojureScript is a free compiler that turns Clojure into JavaScript for browser and Node.js applications. It is best suited to developers who want Clojure’s programming model across JavaScript environments. Choose it for that language fit; look elsewhere if adopting Clojure and its setup is not part of the plan.

Overview

Rather than introducing a new runtime target, ClojureScript translates Clojure source into JavaScript. Its intended reach is client and embedded application development wherever JavaScript runs. The project dates to 2011 and is distributed under the Eclipse Public License 1.0, which covers use and distribution.

Browser output is the default in the quick start; selecting the Node.js target produces Node.js output. REPL support enables interactive development and testing in either a browser or Node.js, an advantage for developers who prefer an iterative workflow. Source-mapped stack traces point to ClojureScript locations, keeping errors closer to the source developers work in.

Key features

Clojure constructs and JavaScript output

The compiler brings Clojure’s rich data structures, functional programming, macros, reader, destructuring, and polymorphism constructs to JavaScript environments. That is a substantial reason to choose it if those constructs are central to how a team wants to write client or embedded software. For a team seeking only a JavaScript-oriented compiler, the need to work in Clojure is a poor trade.

Compilation and dependencies

Its JavaScript output is compatible with Google Closure Compiler advanced compilation, which can minify output and remove dead code. ClojureScript also supports ClojureScript and JavaScript dependencies; the quick start demonstrates React use. These capabilities make it relevant to projects that need JavaScript interoperation, while the advanced compilation option gives teams a way to optimize generated output.

Tooling and documentation

The build ecosystem includes shadow-cljs, Figwheel, Leiningen, and lein-cljsbuild. Editor resources cover Cursive, Emacs, VS Code, Light Table, Sublime Text, Vim, and Atom. This range gives developers several routes into a working setup, though choosing and configuring a build tool and editor remains part of adopting the ecosystem.

API and reference documentation cover compiler and REPL options, dependencies, advanced compilation, source maps, and JavaScript module support. Module support is marked Alpha, so teams that depend on it should account for its status rather than treat it as a settled part of the workflow.

Pricing

ClojureScript is free and open source. Its ClojureScript plan costs nothing and is covered by the Eclipse Public License 1.0. There are no paid tiers or seat charges in the plan described; CLI and API access are both available. This suits individuals and teams evaluating or using the compiler without a software subscription cost, but it does not remove the work of meeting its development prerequisites.

Platforms

The listed platforms are Linux, macOS, Windows, self-hosted, and web. The quick start specifies a browser and Clojure for its main macOS and Linux tutorial. On Windows it specifies Java 21 and the standalone ClojureScript JAR. Node.js is a supported output target, and the quick start describes stable Node.js versions at or above 0.12.X as supported at the time of that page. That qualification matters when choosing a runtime; teams should confirm their target setup before committing.

Who it's for

ClojureScript fits developers and teams who already value Clojure’s functional approach and want to apply it to client or embedded applications that run where JavaScript reaches. REPL workflows and source-mapped stack traces are particularly relevant to developers who prefer interactive development and debugging against ClojureScript source.

It is less compelling for teams that want to stay in JavaScript or that need a mature JavaScript module workflow immediately. The Clojure language choice, platform-specific prerequisites, and Alpha module support are meaningful adoption considerations, not incidental setup details.

Pros and cons

Pro: Clojure data structures and language constructs compile to JavaScript, making the same language model usable in browser and Node.js contexts.

Pro: REPL support and source-mapped stack traces support an interactive workflow with errors mapped back to ClojureScript source locations.

Pro: Advanced compilation compatibility can minify output and eliminate dead code, and the compiler supports both ClojureScript and JavaScript dependencies.

Con: Adopting ClojureScript means taking on Clojure and its setup requirements; it is not a natural choice for teams seeking a JavaScript-native workflow.

Con: JavaScript module support is marked Alpha, which makes it a weaker fit where that capability must be dependable now.

Con: The quick start gives different prerequisites by platform, and its stated Node.js support floor is tied to the version described on that page.

Alternatives

For a broader directory of compiler choices, see Code Transpilers.

JSweet is a free, open-source Java-to-JavaScript transpiler; choose it when Java, rather than Clojure, is the desired source language.

SWC is a free, open-source Rust-based developer toolchain; it is an option for teams looking for that kind of toolchain rather than Clojure-to-JavaScript compilation.

Google Web Toolkit is a free, open-source option under Apache 2.0; consider it as an alternative compiler choice for web development.

Kotlin/JS is a free Kotlin compiler target for JavaScript configured with the Kotlin Multiplatform Gradle plugin; choose it when Kotlin is the source language you want to target JavaScript.

Transcrypt is free and open source under Apache 2.0; consider it when that compiler is a better fit for your project.

Babel is free, community funded, and has no paid tiers or stated usage limits; choose it when that option better suits the project’s compiler needs.

Scala.js is a free Scala-to-JavaScript compiler managed through a Scala build tool; choose it when Scala is the language your team wants to compile to JavaScript.

Cython is free under the Apache 2.0 open-source license; consider it as another open-source compiler option.

Verdict

ClojureScript is a strong choice for developers who want Clojure’s language features in applications that run on JavaScript, especially when REPL-based development and source-mapped debugging suit their workflow. Its free, open-source plan removes subscription cost, but not the learning and setup commitment. Choose another compiler if your team wants a JavaScript-native workflow or relies on JavaScript module support that is beyond Alpha.