Frontend developer for small website fixes (Advanced JavaScript and CSS needed)

I'm looking for a frontend developer to write JavaScript functions that create previews of website changes before they are fully implemented. The work involves small updates to client websites. Clients want to preview the changes first, and once they approve them, we move forward with the actual implementation. You should have a solid understanding of vanilla JavaScript, HTML, and CSS. The code will be written as native JavaScript inside a single wrapper function that runs in the Google Chrome console and is used only to generate an instant preview. The tasks are very small and straightforward, and each task is limited to a single page and can be finished in 15-30 minutes. You may use AI tools as well, but you must review and test the code carefully before submitting it. This position has the potential to become a long-term opportunity.