Metric-imperial converter microservice

I created this app as a requirement for my freeCodeCamp Information Security and Quality Assurance Certification, using Node.js, Express, and Chai. The front end API test on the home page also uses Bootstrap, jQuery, and highlight.js.

You can read the unit and functional tests I wrote on GitHub or Glitch. To run the tests yourself, fork/remix this project, create a .env file containing NODE_ENV="test", start the server, and look at the server console logs.

This project fulfills the following user stories:

1. I will help prevent the client from trying to guess (sniff) the MIME type.
2. I will prevent cross-site scripting (XSS) attacks.
3. I can GET /api/convert with a single parameter containing an accepted number and unit and have it converted.
4. Hint: Split the input by looking for the index of the first character.
5. I can convert 'gal' to 'L' and vice versa. (1 gal to 3.78541 L)
6. I can convert 'lbs' to 'kg' and vice versa. (1 lbs to 0.453592 kg)
7. I can convert 'mi' to 'km' and vice versa. (1 mi to 1.60934 km)
8. If my unit of measurement is invalid, returned will be 'invalid unit'.
9. If my number is invalid, returned with will 'invalid number'.
10. If both are invalid, return will be 'invalid number and unit'.
11. I can use fractions, decimals or both in my parameter (e.g., 5, 1/2, 2.5/6), but if nothing is provided it will default to 1.
12. My return will consist of the initNum, initUnit, returnNum, returnUnit, and string spelling out units in format {initNum} {initial_Units} converts to {returnNum} {return_Units} with the result rounded to 5 decimals.
13. All 16 unit tests are complete and passing.
14. All 5 functional tests are complete and passing.