🏀 The premier single-player basketball management simulation game, made entirely in client-side JavaScript.
JavaScript Other


Basketball GM 4.1.0

A single-player basketball simulation game. Make trades, set rosters, draft players, and try to build the next dynasty, all from within your web browser. The game is implemented entirely in client-side JavaScript, backed by IndexedDB.

Copyright (C) Jeremy Scheff. All rights reserved.

Basketball GM is NOT open source, but it is also not completely closed. Please see LICENSE.md for details.

Development Info

If you just want to play the game, go to http://basketball-gm.com/. Instructions below are for developers who want to run a copy locally so they can make changes to the code.

If you want to contribute but get stuck somewhere, please contact me! I'm happy to help.

License and Contributor License Agreement

Basketball GM is NOT open source, but it is also not completely closed. Please see LICENSE.md for details.

If you want to contribute code to Basketball GM, you must sign a contributor license agreement. There are separate forms for individuals and entities (such as corporations):

Make a copy of the form, fill in your information at the bottom, and send an email to commissioner@basketball-gm.com with the subject line, "Contributor License Agreement from YOUR_NAME_HERE (GITHUB_USERNAME_HERE)".

Step 1 - Installing

First, make sure you're using Node.js v6 or higher, older versions probably won't work. Then, all of the tooling used in development can be set up by simply installing yarn and running


from within this folder.

Step 2 - Building

Basketball GM uses Browserify for JS minification and clean-css for CSS minification. To build the app along with all its assets, run

yarn run build

However during development, you probably would rather do

yarn run start-watch

which will start the server and watch JS and CSS files for changes and recompile. This simply runs both yarn run start and yarn run watch together, which alternatively can be run separately if you wish.

Open package.json to see all available scripts.

Step 3 - Running

To run the game locally, you need some way of running a web server to display the content. There are currently two ways to do it. It doesn't matter which you use as long as you can get it to run on your computer.

1. Node.js (easiest)


yarn run start

and point your browser to http://localhost:3000/. If you use the command yarn run start-watch from above, then running the command yarn run start is not necessary.

2. Apache

The mod_rewrite rules in .htaccess can be used to make Apache run Basketball GM. Everything should work if you point it at the build folder with mod_rewrite enabled. That's how it's done on play.basketball-gm.com.

Step 4 - Testing

ESLint, Flow, and, stylelint are used to enforce some coding standards. To run them on the entire codebase, run

yarn run lint

Integration and unit tests are bunched together in the js/test folder. Coverage is not great. They can be run from the command line in Karma with

yarn test


yarn run test-watch

Code Overview

Basketball GM is a single-page app that runs almost entirely client-side by storing data in IndexedDB. The core of the game runs inside a Shared Worker (or a Web Worker in crappy browsers that don't support Shared Workers), and then each open tab runs only UI code that talks to the worker. The UI code is in the src/js/ui folder and the core game code is in the src/js/worker folder. They communicate through the toUI and toWorker functions.

The UI is built with React and Bootstrap.

In the worker, data is ultimately stored in IndexedDB, but for performance and cross-browser compatibility reasons, a cache (implemented in src/js/worker/db/Cache.js) sits on top of the database containing all commonly accessed data. The idea is that IndexedDB should only be accessed for uncommon situations, like viewing stats from past seasons. For simulating games and viewing current data, only the cache should be necessary.

The cache is overly complicated because (1) the values it returns are mutable, so you better not mess with them accidentally, and (2) when you do purposely mutate a value (like updating a player's stats), you need to remember to always write it back to the cache manually by calling idb.cache.*.put.

Also in the worker, there is a global variable self.bbgm which gives you access to many of the internal functions of Basketball GM from within your browser.

Git Workflow

If you want to contribute changes back to the project, first create a fork on GitHub. Then make your changes in a new branch. Confirm that the tests (hopefully including new ones you wrote!) and ESLint all pass. Finally, send me a pull request.

It's also probably a good idea to create an issue on GitHub before you start working on something to keep me in the loop.

Less Important Development Info


Basketball GM's layout is currently based on Bootstrap 3.1.1 with the following options:

  • @font-size-base set to 13px

Basketball stuff

Abbreviations of stats should be done like basketball-reference.com stat pages. For instance, "defensive rebounds" is "drb".


The game runs equally well within a web browser and within Cordova (Android 4.4+). The codebase is designed to handle both situations (the main difference is absolute vs relative paths, governed by window.inCordova in index.html).

Warning: This hasn't been tested in a while and is probably broken by now.

Thank you BrowserStack

Shout out to BrowserStack for helping with cross-browser testing.