JavaScipt Toollbox for chess programming. It can tag, play, import and export PGN and FEN and validate moves.
cm-chess is like chess.js, but in ECMA-Script 6 (ES 6) and it can store and process different move variations, Nags and Annotations. cm-chess is the basis for the further chess projects.
I run the online chess server chessmail. The system has been running for over 17 years and is constantly being further developed.
chessmail is cool, try it out!