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Dashboard webapp for display on a wall-mounted tablet or screen.

Getting Started

Discussed in detail in this blog series.

Project Overview

Directory structure

  • /: project config files
  • .clj-kondo/: lint config and cache files (cache files are not tracked; see .gitignore)
  • dev/: source files compiled only with the dev profile
  • resources/public/: SPA root directory; dev / prod profile depends on the most recent build
    • index.html: SPA home page
      • Dynamic SPA content rendered in the following div:
        <div id="app"></div>
      • Customizable; add headers, footers, links to other scripts and styles, etc.
    • Generated directories and files
      • Created on build with either the dev or prod profile
      • Deleted on lein clean (run by all lein aliases before building)
      • js/compiled/: compiled CLJS (shadow-cljs)
  • src/cljs/cockpit/: SPA source files (ClojureScript, re-frame)
    • core.cljs: contains the SPA entry point, init
  • test/cljs/cockpit/: test files (ClojureScript, cljs.test)
    • Only namespaces ending in -test (files *_test.cljs) are compiled and sent to the test runner


Use your preferred editor or IDE that supports Clojure/ClojureScript development. See Clojure tools for some popular options.

Environment Setup

  1. Install JDK 8 or later (Java Development Kit)
  2. Install Leiningen (Clojure/ClojureScript project task & dependency management)
  3. Install Node.js (JavaScript runtime environment)
  4. Install karma-cli (test runner):
    npm install -g karma-cli
  5. Install Chrome or Chromium version 59 or later (headless test environment)
    • For Chromium, set the CHROME_BIN environment variable in your shell to the command that launches Chromium. For example, in Ubuntu, add the following line to your .bashrc:
      export CHROME_BIN=chromium-browser
  6. Install clj-kondo (linter)
  7. Clone this repo and open a terminal in the cockpit project root directory
  8. Download project dependencies:
    lein deps && npm install
  9. Setup lint cache:
    clj-kondo --lint "$(lein classpath)"
  10. Setup linting in your editor

Browser Setup

Browser caching should be disabled when developer tools are open to prevent interference with shadow-cljs hot reloading.

Custom formatters must be enabled in the browser before CLJS DevTools can display ClojureScript data in the console in a more readable way.


  1. Open DevTools (Linux/Windows: F12 or Ctrl-Shift-I; macOS: ⌘-Option-I)
  2. Open DevTools Settings (Linux/Windows: ? or F1; macOS: ? or Fn+F1)
  3. Select Preferences in the navigation menu on the left, if it is not already selected
  4. Under the Network heading, enable the Disable cache (while DevTools is open) option
  5. Under the Console heading, enable the Enable custom formatters option


  1. Open Developer Tools (Linux/Windows: F12 or Ctrl-Shift-I; macOS: ⌘-Option-I)
  2. Open Developer Tools Settings (Linux/macOS/Windows: F1)
  3. Under the Advanced settings heading, enable the Disable HTTP Cache (when toolbox is open) option

Unfortunately, Firefox does not yet support custom formatters in their devtools. For updates, follow the enhancement request in their bug tracker: 1262914 - Add support for Custom Formatters in devtools.


Running the App

Start a temporary local web server, build the app with the dev profile, and serve the app with hot reload:

lein dev

Please be patient; it may take over 20 seconds to see any output, and over 40 seconds to complete.

When [:app] Build completed appears in the output, browse to http://localhost:8280/.

shadow-cljs will automatically push ClojureScript code changes to your browser on save. To prevent a few common issues, see Hot Reload in ClojureScript: Things to avoid.

Opening the app in your browser starts a ClojureScript browser REPL, to which you may now connect.

Connecting to the browser REPL from Emacs with CIDER

Connect to the browser REPL:

M-x cider-jack-in-cljs

See Shadow CLJS User's Guide: Emacs/CIDER for more information. Note that the mentioned .dir-locals.el file has already been created for you.

Connecting to the browser REPL from other editors

See Shadow CLJS User's Guide: Editor Integration. Note that lein dev runs shadow-cljs watch for you, and that this project's running build id is app, or the keyword :app in a Clojure context.

Alternatively, search the web for info on connecting to a shadow-cljs ClojureScript browser REPL from your editor and configuration.

For example, in Vim / Neovim with fireplace.vim

  1. Open a .cljs file in the project to activate fireplace.vim
  2. In normal mode, execute the Piggieback command with this project's running build id, :app:
    :Piggieback :app

Connecting to the browser REPL from a terminal

  1. Connect to the shadow-cljs nREPL:

    lein repl :connect localhost:8777

    The REPL prompt, shadow.user=>, indicates that is a Clojure REPL, not ClojureScript.

  2. In the REPL, switch the session to this project's running build id, :app:

    (shadow.cljs.devtools.api/nrepl-select :app)

    The REPL prompt changes to cljs.user=>, indicating that this is now a ClojureScript REPL.

  3. See user.cljs for symbols that are immediately accessible in the REPL without needing to require.

Running Tests

Build the app with the prod profile, start a temporary local web server, launch headless Chrome/Chromium, run tests, and stop the web server:

lein karma

Please be patient; it may take over 15 seconds to see any output, and over 25 seconds to complete.

Running shadow-cljs Actions

See a list of shadow-cljs CLI actions:

lein run -m shadow.cljs.devtools.cli --help

Please be patient; it may take over 10 seconds to see any output. Also note that some actions shown may not actually be supported, outputting "Unknown action." when run.

Run a shadow-cljs action on this project's build id (without the colon, just app):

lein run -m shadow.cljs.devtools.cli <action> app

Debug Logging

The debug? variable in config.cljs defaults to true in dev builds, and false in prod builds.

Use debug? for logging or other tasks that should run only on dev builds:

(ns cockpit.example
  (:require [cockpit.config :as config])

(when config/debug?
  (println "This message will appear in the browser console only on dev builds."))


Build the app with the prod profile:

lein prod

Please be patient; it may take over 15 seconds to see any output, and over 30 seconds to complete.

The resources/public/js/compiled directory is created, containing the compiled app.js and manifest.edn files.

The resources/public directory contains the complete, production web front end of your app.

Always inspect the resources/public/js/compiled directory prior to deploying the app. Running any lein alias in this project after lein dev will, at the very least, run lein clean, which deletes this generated directory. Further, running lein dev will generate many, much larger development versions of the files in this directory.


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