A Javascript chess engine inspired by Fabien Letouzey's Fruit 2.1. Try her here:-

https://op12no2.github.io/lozza-ui

All you need is lozza.js from repo root.

Here is a little example to do a 10 ply search:-

var lozza = new Worker('lozza.js');

lozza.onmessage = function (e) {
  $('#dump').append(e.data);             //assuming jquery and a div called #dump
                                         //parse messages from here as required
};

lozza.postMessage('uci');                // lozza uses the uci communication protocol
lozza.postMessage('ucinewgame');         // reset tt
lozza.postMessage('position startpos');
lozza.postMessage('go depth 10');        // 10 ply search

Try this example here:-

https://op12no2.github.io/lozza-ui/ex.htm

Please note that Lozza's code is folded using {{{ and }}} (emacs convention) and most easily read using an editor with a folding capability.

A sister repo has more web-based examples for playing and analysing etc. with Lozza.

https://github.com/op12no2/lozza-ui

You can try them here:-

https://op12no2.github.io/lozza-ui

As a UCI engine Lozza can be used in popular chesss user interfaces like Banksia, Winboard, Arena and CuteChess. Download the latest release and then follow the instructions in the readme.txt file. Any platform that supports Node.js can be targetted.

https://github.com/op12no2/lozza/releases

Lozza accesses stdio via Node.js and will run on any platfrom that supports Node.js. To type UCI commands into Lozza, start Node.js with lozza.js or lozza as the parameter and then enter UCI commands. Look at the lozUCI class in lozza.js for the subset of UCI implemented and some command extensions. For example:-

> node lozza
ucinewgame
position startpos
eval
go depth 10
quit

Commands can also be given on invocation, for example:-

> node lozza ucinewgame bench "position startpos" board "go movetime 100" quit

NB: bench does a cumulative node count while searching a list of FENs, displaying the total and the time it took. It's particularly useful when checking that changes that should not affect searching have in fact not affected searching.

https://www.chessprogramming.org/Fruit - Fruit

https://www.chessprogramming.org/Main_Page - Chess programming wiki

https://computerchess.org.uk/ccrl/4040/ - CCRL rating list

https://www.wbec-ridderkerk.nl/html/UCIProtocol.html - UCI protocol