Import and Export in JavaScript (and other links)

 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/export

misc:

https://stackoverflow.com/questions/28725955/how-do-i-test-a-single-file-using-jest

https://stackoverflow.com/questions/19578796/what-is-the-save-option-for-npm-install

https://jestjs.io/docs/getting-started

https://siddharthac6.medium.com/json-web-token-jwt-the-right-way-of-implementing-with-node-js-65b8915d550e

https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Object_prototypes