Note that it's not the smallest engine, but the engine that is even smaller than Micro-max plays awful chess (dropping pieces) and even walk into check (illegal move).
Lozza-js is rated around 2300, and is about twice the size of Garbochess-JS.
Toledo Nanochess and P4wn are probably less than 2000 elo, and Stockfish-js is considerably larger than Garbochess and Lozza.
t seems like garbo was a little stronger maybe 2670 but anywhoo.
https://jtiscione.github.io/chessboard3js/play.html is a nice online interface for playing p4wn -weak lozzo -strong!! and stockfish -godlike
http://forwardcoding.com/projects/ajaxchess/chess.html <--garbo chess
http://htmlchess.sourceforge.net/demo/example.html <-- 2d-3d chess