This is how the Dash Button code is organized, so you can understand where to make changes and how to test your code.
The source files are under src and are written using TypeScript.
The source files are compiled with tsc to a version of JavaScript that Node.js understands. These compiled files go in a directory called build, which is not committed to Git but is published to npm.
The easiest way to run tsc is to run npm run build or npm run watch. Both of these compile the TypeScript in src and output it in build, but the watch command will keep watching your filesystem for any changes and compile files when you save them. It's recommended when you are developing.
The unit tests run with Jest since it focuses on automocking, which is great for Dash Button since we want to mock the pcap library. Look under src/__tests__ for the test files and run them with npm test. You can pass options to Jest after -- in the npm command; to have Jest re-run the tests when a file changes, run npm test -- --watch.
Manually test the CLI by running sudo node build/cli.js.
Most contributors don't have to think about publishing since that's the responsibility of the package owners. These instructions are for owners:
Before publishing, npm will automatically run the prepublish script, which cleans the build directory and recompiles all of the source files. Then just the build files are uploaded to npm and the new version is made available.