mediasoup-client is a JavaScript library for building mediasoup based client side applications (such as web applications). It's a tiny library exposing a powerful cross-browser API and supports all current WebRTC browsers via different handlers for each model/version.
There is no native WebRTC or RTP engine in Node.js. When running in Node.js the application must provide mediasoup-client with a custom handler to control a 3rd party media/RTP library.