https://github.com/tanakahisateru/js-markdown-extra
Promising in terms of functionality, but still very buggy and currently has a slow rate of development.
https://leeoniya.github.io/reMarked.js/
Definitely worth considering. (Also: nice page of links.)
https://github.com/jmcmanus/pagedown-extra
Has a good list of desirable functionality, but far too heavyweight, as proved by the time it takes to render its homepage.
https://github.com/showdownjs/showdown
At present this looks like the dog's nads:
- Under active development.
- Seems to have all the functionality I want.
- Has great performance (compared to other client-side options).
- Seems surprisingly clutter-free and open to extension.
- Already has integration with Angular if I want that later.