https://simple-sudoku-ts.netlify.app/
This is a remake of https://github.com/harchcode/sudokujs, using Typescript instead of old Javascript, and not making it as a library. I also don't know why the demo of that repo become broken, maybe because of browser update as that was developed on around 2012.
I forgot where I got the generator algorithm, and I can't find it anywhere. I was so young back then I didn't even care about mentioning the source. If you happen to know where is that algorithm coming from, please let me know.