Leeze.js allows developers to create reactive websites without the need of transpiling, building or bundling steps, in a single small JS file. Just add the script to your pages and you're good to go.
You can check out the getting started documentation here.
Feel free to open issues or pull requests to submit a bug or improve Leeze.js! Keep in mind that this project's main focus is not open source, so any contribution could be discarded or rejected based on its feasibility or current project plans.