Running ClojureScript on Node.js

First install Node.js. For instructions on installing Node.js, see the Node.js wiki. Only the current stable versions of Node.js (>= 0.12.X) are supported at this time. Your src/hello_world/core.cljs should look like the following:

(ns hello-world.core
  (:require [cljs.nodejs :as nodejs]))

(nodejs/enable-util-print!)

(defn -main [& args]
  (println "Hello world!"))

(set! *main-cli-fn* -main)

Make a build helper file called node.clj:

(require 'cljs.build.api)

(cljs.build.api/build "src"
  {:main 'hello-world.core
   :output-to "main.js"
   :target :nodejs})

The only differences are that we had to specify a :nodejs target and we do not output main.js to the out directory. This is important due to the way that Node.js resolves JavaScript source files.

Node.js has great source mapping support, in order to enable it just install source-map-support:

npm install source-map-support

Let's build your Node project:

java -cp cljs.jar:src clojure.main node.clj

You can run your file with:

node main.js

Note: Under Node.js there is little reason to use advanced optimizations. While advanced optimizations does apply performance related optimizations, these are now largely obviated by optimizations present in modern JavaScript virtual machines like V8, SpiderMonkey, and JavaScriptCore. For Node.js, :simple or :none optimizations suffice and using them removes the need for extra steps like supplying an externs file.

Node.js REPL

Running a Node.js REPL is much simpler than running a browser REPL. Create a helper build file called node_repl.clj that looks like the following:

(require 'cljs.repl)
(require 'cljs.build.api)
(require 'cljs.repl.node)

(cljs.build.api/build "src"
  {:main 'hello-world.core
   :output-to "out/main.js"
   :verbose true})

(cljs.repl/repl (cljs.repl.node/repl-env)
  :watch "src"
  :output-dir "out")

There's no need to add any REPL specific bits to src/hello_world/core.cljs, make sure it looks as described in the previous section.

Let's start the REPL:

rlwrap java -cp cljs.jar:src clojure.main node_repl.clj

All the previously described REPL interactions for the browser should work.

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