Still not sure how would SEO work in hashnode's case? When I disable java script in my browser, nothing comes back from server except static assets.

This one Pace.JS is just start and forget. It will capture any http request and start and end by itself. You still can optionally show the progress bar and hide it manually. It also comes with different themes for the progress animation.

SweetAlert2 was forked off the original one you mentioned but more functionalties limonte.github.io/sweetalert2

This one is built on top of CKEditor: alloyeditor And this gist shows how to use it with React AlloyEditor as React module