cljamClojure for JavaScript

Run Clojure right now ​

The snippet below is evaluated by cljam in your browser when you press Run. Edit it, re-run it, break it. It's the same interpreter that ships on npm.

Try editing the Playground for a full Monaco-powered REPL with multi-form evaluation, persistent state, and sample files.

Embed it in JavaScript ​

Drop a Clojure runtime into any JS/TS project. createSession() returns a plain object. Evaluate strings, hand the same session to an editor, give it to a tool call.

import { createSession, printString, nodePreset } from '@regibyte/cljam'

const session = createSession({ ...nodePreset() })

const result = session.evaluate('(map inc [1 2 3])')
console.log(printString(result))
// => (2 3 4)

Inject your own host APIs through hostBindings and Clojure code can call straight into your TypeScript world. See the Embedding guide for the full surface.

Or open a REPL and connect your editor ​

cljam ships a real nREPL server, the same protocol Clojure tooling speaks officially. Install once, run once, and Calva / CIDER / Cursive will treat your Node or Bun process like any other Clojure runtime.

npm install -g @regibyte/cljam
cljam nrepl-server --port 7889 --root-dir .

Now evaluate forms straight from your editor against a live JavaScript process. Pair this with cljam-mcp and an LLM gets the same view of the same session you do.

A small but growing library ecosystem ​

(require '[cljam.schema.core   :as s]
         '[cljam.date          :as date]
         '[cljam.integrant     :as ig])

(s/validate [:map [:name :string] [:age :int]]
            {:name "John Doe" :age 36})
;; => {:ok true :value {:name "John Doe" :age 36}}

(date/format (date/now) "de-DE" {:year "numeric" :month "long" :day "numeric"})
;; => "17. April 2026" (formatted date string)

Each library is a regular npm package under the @regibyte scope. Build your own with cljam gen-lib-source. See the Building Libraries guide.