chess-es6.js is a rewrite of ~jhlywa's chess.js in es6, a newer version of Javascript.
It also includes the ability to parse PGN variations, as well as traverse the move tree and add new lines of play.
chess-es6.js can be transpiled down to es5 for peformant use in most web browsers.
Demo site: http://chessdemo.herokuapp.com
Demo site's repo: http://github.com/aaronfi/chess-es6-demo
A more detailed README file is coming soon.