During Hacktoberfest, a developer made their third pull request by contributing to an open-source weather app called Whtrapp. The project aimed to add an autocomplete feature to the search bar for cities, as requested in Issue #18. The developer successfully implemented the feature, which suggests city names based on user input and updates as they type more letters. To ensure code modularity and minimize potential conflicts, the developer created a separate file for the new feature and exported it to the main JavaScript file.

Source: https://dev.to/aldrin312/3rd-pull-request-hacktoberfest-5cm6