EbookLib-JS is a Javascript library for managing EPUB2/EPUB3 files. It's a Javascript implementation of the Python library, EbookLib. EbookLib-JS is compatible both server-side and in a browser.
Additional documentation is available here
Note: Reading EPUB files isn't currently implemented. This is a planned feature though to make EbookLib-JS feature comparable with EbookLib.
npm install ebooklib-js
EbookLib-JS is licensed under the AGPL license.