What can I use javascript except for web development?

Answer 1

JavaScript is a high-level dynamic interpreted programming language that allows client-side scripting to create completely dynamic web applications and websites.
It is very light weight prototype based language which can easily run on the browers.
Beign a multi-paradigm and weekly typed script It can provide  brilliant power to your webpage.
Using JavaScript you can put calculations, logical conditions and all the programming functionality.

Answer 2

Desktop applications as well.

Answer 3

Everything. Javascript is a full blown programming language (turing complete), so you can code whatever you like. But some problems are easier to solve with other languages (that support different programming paradigms).