The book tells about the programming language j & # 097; vascript, the development of both general-purpose programs running in the Node.js environment and scripts for web pages. The basics of j & # 097; vascript are given: data types, operators, working with numbers, strings, date and time, arrays, functions, classes (both old and new syntax), iterators, generators and the Promise class. Explained how to work with the debugger built into the Visual Studio Code editor. It tells about modules, tools for working with the file system and programming web servers. Document object model is described. Tools for working with elements of a web page, the page itself and the browser, AJAX technology (including the Fetch API), as well as ready-made software packages for developing websites, in particular Webpack, are considered. With the advent of Node.js, it became possible to write programs of almost any purpose in j & # 097; vascript: tool and system utilities, servers, and even applications with a graphical interface (although this will require additional libraries). The book offered to the readers' attention tells about the j & # 097; vascript language, its application for writing both programs running Node.js and scripts executed by web browsers. In fact, this is a comprehensive guide for j & # 097; vascript programmers who want to know everything about this language.