Are you aware of Node.js? There is no doubt about the increasing reach of JavaScript in every area of web development. Node.js is another extension of JavaScript and it can be explained as a runtime system whose main application is to create server-side apps. It is highly popular among Java Coders to create real-time APIs for different web development projects. Node.js is not exactly JavaScript. It is an open-source platform with a SSJS run-time environment and capability to handle I/O in a non-blocking manner. You need to install node.js in your system before running or using it for different purposes.
If you are planning to understand Node.js in a better manner, here are some excellent books to get in touch with this technology.