Try the app here: https://whimsical-selkie-fd3433.netlify.app/
(October 2023) The above netlify link still works. Essentially this project is an adaptation to my previous build-it-yourself-bitcoin app, but this time using React and a new front-end UI design. Since then I've incorporated this concept into a full fledged crypto wallet called ARTSNL.
A DIY bitcoin transaction builder built with React.
For a more detailed README, refer to my other repository of a similar app built using ExpressJS here.