Show HN: hakk -- a REPL for developing Node.js programs on the fly

hakk is a new REPL-based tool for developing Node.js programs. hakk runs your .js source files, and updates your program as it runs whenever you make a change. Unlike the built-in node repl, hakk lets you re-define consts, functions, and class members while your code is running. It works with any code editor.

I would love to get feedback. Do you find this tool useful? What improvements would you like to see?