zMIDI is a JavaScript library that allows you to receive message froms connected musical equipment (supporting the MIDI protocol) and making it available inside the web browser.
zMIDI uses the Web MIDI API, which is currently supported in Google Chrome, Microsoft Edge and Opera, making it a niche functionality, though support could grow over time.
Who / what is using it ?
zMIDI was written specifically for WebSID and later integrated in Efflux. In both apps zMIDI listens to incoming note messages allowing you to instantly play and record notes with a connected keyboard. Additionally, Efflux also maps CC controller messages to allow tweaking of various sound shaping parameters.
Available via npm
npm install zmidi