vditor

Markdown ，（）、（ Typora）。An In-browser Markdown editor, support WYSIWYG (Rich Text), Instant Rendering (Typora-like) and Split View modes. Maintained by Vanessa219 on GitHub, where it has earned 11,139 stars from the community.

It's actively developed around commonmark, editor, gfm, and is a solid reference for anyone building with these tools.