What is clojurescript?

ClojureScript is a version of the Clojure programming language that compiles to JavaScript. It lets you write code using Clojure’s simple, functional style, and then runs that code in any web browser or JavaScript environment.

Let's break it down

  • Clojure: a modern, Lisp‑style language that runs on the Java Virtual Machine. It emphasizes immutable data and functions.
  • Script: means the code is turned into JavaScript, the language browsers understand.
  • Compiler: a tool called “shadow-cljs” or “lein-cljsbuild” reads your ClojureScript files and produces JavaScript files.
  • Result: you get a web app (or Node.js script) written in Clojure’s syntax but executed as normal JavaScript.

Why does it matter?

Because it gives developers the power of Clojure’s clean, concise syntax and strong functional concepts while still being able to run everywhere JavaScript runs. It reduces bugs (thanks to immutable data), makes code easier to reason about, and lets you share libraries between server‑side Clojure and client‑side ClojureScript.

Where is it used?

  • Interactive web front‑ends and single‑page applications.
  • Mobile apps built with React Native (using Reagent or Rum).
  • Data‑visualisation dashboards (e.g., with D3 via cljsjs).
  • Game prototypes and educational tools.
  • Some companies use it for internal tools, e‑commerce sites, and real‑time collaboration apps.

Good things about it

  • Simple syntax: very little boilerplate, thanks to Lisp’s parentheses.
  • Immutable data structures: fewer side‑effects, easier debugging.
  • Rich REPL: you can interactively test code in the browser.
  • Seamless interop: call any existing JavaScript library directly.
  • Shared code: same language can be used on server (Clojure) and client (ClojureScript).

Not-so-good things

  • Learning curve: Lisp parentheses and functional concepts can feel odd at first.
  • Tooling fragmentation: multiple build tools (shadow-cljs, figwheel, lein) can be confusing.
  • Smaller community: fewer tutorials and libraries compared to plain JavaScript or TypeScript.
  • Debugging: stack traces are often in generated JavaScript, making them harder to read.
  • Compilation time: large projects may have slower compile cycles than native JavaScript.