I contributed to two packages to Webhint.io, a NodeJS CLI tool that tests websites for accessibility, speed, compatibility and more. The first package checked if a website has a valid doctype declaration, the second checked for CSS compatibility.
For the hint-doctype package, I worked with another developer to come up with the strategy for the algorithm. I then implemented the algorithm and wrote the tests.
The hint-compat-api package was a much larger package, and three developers worked on it. I wrote one of the core algorithms, wrote the tests and fixed bugs in the overall code of the package. The algorithm I wrote checked for browser compatibility of different CSS rules with the help of a CSS parser utilising PostCSS.