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npm Clojars Project

shadow-cljs provides everything you need to compile your ClojureScript code with a focus on simplicity and ease of use.

User's Guide | Quick Start | Tutorials | Browser Extension

Features

overview-img

Requirements

Quick Start

Creating your project can be done quickly using the npx create-cljs-project utility. npx is part of npm and lets us run utility scripts quickly without worrying about installing them first. The installer will create a basic project scaffold and install the latest version of shadow-cljs in the project.

$ npx create-cljs-project acme-app
npx: installed 1 in 5.887s
shadow-cljs - creating project: .../acme-app
Creating: .../acme-app/package.json
Creating: .../acme-app/shadow-cljs.edn
Creating: .../acme-app/.gitignore
Creating: .../acme-app/src/main
Creating: .../acme-app/src/test
----
Installing shadow-cljs in project.

npm notice created a lockfile as package-lock.json. You should commit this file.
+ shadow-cljs@<version>
added 88 packages from 103 contributors and audited 636 packages in 6.287s
found 0 vulnerabilities

----
Done.
----

The resulting project has the following structure

.
├── node_modules (omitted ...)
├── package.json
├── package-lock.json
├── shadow-cljs.edn
└── src
    ├── main
    └── test

shadow-cljs.edn will be used to configure your CLJS builds and CLJS dependencies. package.json is used by npm to manage JS dependencies.

Everything is ready to go if you just want to start playing with a REPL

$ npx shadow-cljs node-repl
# or
$ npx shadow-cljs browser-repl

When building actual projects we need to configure the build first and create at least one source file.

The default source paths are configured to use src/main as the primary source directory. It is recommended to follow the Java Naming Conventions to organize your CLJS namespaces. It is recommended to start all namespaces with a unique enough prefix (eg. company name, project name) to avoid conflicts with generic names such as app.core. Suppose you were building a Web Frontend for Acme Inc. using acme.frontend.app might be a good starting point as it can easily grow to include acme.backend.* later on.

Using the above example the expected filename for acme.frontend.app is src/main/acme/frontend/app.cljs.

Lets start with a simple example for a browser-based build.

(ns acme.frontend.app)

(defn init []
  (println "Hello World"))

Inside the shadow-cljs.edn :builds section add

{...
 :builds
 {:frontend
  {:target :browser
   :modules {:main {:init-fn acme.frontend.app/init}}
   }}}

This config tells the compiler to call (acme.frontend.app/init) when the generated JS code is loaded. Since no :output-dir is configured the default public/js is used. You can start the development process by running:

$ npx shadow-cljs watch frontend
...
a few moments later ...
...
[:frontend] Build completed. (134 files, 35 compiled, 0 warnings, 5.80s)

The compilation will create the public/js/main.js we configured above (:main becomes main.js in the :output-dir). Since we want to load this in the browser we need to create a HTML file in public/index.html.

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>acme frontend</title>
  </head>
  <body>
    <div id="root"></div>
    <script src="/js/main.js"></script>
  </body>
</html>

We also need a simple HTTP server to serve our HTML since modern Browsers all place a few restrictions on files loaded directly from disk which will lead to issues later. shadow-cljs provides such a server but you can use anything you like at this point. It only matters that the files from the public directory are served properly. To start the built-in web server just adjust the build config from above.

{...
 :dev-http {8080 "public"}
 :builds
 {:frontend
  {:target :browser
   :modules {:main {:init-fn acme.frontend.app/init}}
   }}}

Once the config is saved the server will automatically start and serve the content at http://localhost:8080. There is no need to restart shadow-cljs. When opening the above URL the Browser Console should show "Hello World".

To be continued ...

Documentation

Please refer to the User Manual. (Work in Progress)

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License

Copyright © 2024 Thomas Heller

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.