ideone.com : Ideone is an online compiler and debugging tool which allows youto compile source code and execute it online in more than 60 programming languages.
repl.it : Powerful and simple online compiler, IDE, interpreter, and REPL. Code, compile, and run code in 30+ programming languages. including JavaScript, Pytho...
Online javascript beautifier : Beautify, unpack or deobfuscate JavaScript and HTML, make JSON/JSONP readable, etc.
Comby : Comby is a tool for matching and rewriting code.
