This document discusses enabling real-time communication capabilities on the web through JavaScript and WebRTC. It introduces several JavaScript libraries like SIP.js and sipML5 that provide WebRTC capabilities and can integrate with SIP backends to enable audio and video calling functionality in web applications. The document also discusses WebRTC gateways like Janus that can connect WebRTC to other protocols and provides examples of initializing libraries and placing WebRTC calls through them to build real-time communication features into web apps.