Simplest Markdown Editor with Pure JavaScript – easyMarkdown
easyMarkdown is a standalone JavaScript library for converting a normal textarea into a WYSIWYG markdown editor.
JavaScript & CSS markdown
Simple Extendable WYSIWYG Markdown Editor – mditor
mditor is a simple, clean, easy-to-extend and WYSIWYG-style markdown editor that works on both client side or server side.
Lightweight Markdown Parser & Editor In JavaScript – WriteDown
WriteDown is a lightweight JavaScript markdown parser used to create a markdown editor with live preview on your website.