Maybe not quite what you're after, but Bassoon Tracker is written in Javascript, runs in a webpage without installation and has access to thousands of mod files

Maybe not quite what you're after, but Bassoon Tracker is written in Javascript, runs in a webpage without installation and has access to thousands of mod files in modarchive and modules.pl, including their samples: https://www.stef.be/bassoontracker/ https://www.stef.be/bassoontracker/