See sample button file at buttons/sqrt2.btn. It has simple format:

OPERATION DATA ;INLINE COMMENT

Whole line comments also start with ;

$ node src/index.js 'your-button-file'

$ npm run sqrt2

Verify its result in BX register

Only one test, I'm still learning ava.

$ npm install
$ npm test

buttons.js is copyrighted by Zedshaw

https://git.learnjsthehardway.com/learn-javascript-the-hard-way/buttons-computer/