I want to be able to edit existing JS files using pythonic whitespace like CoffeeScript, but output JS that matches the original coding conventions and is indistinguishable from hand-written code. I'd like to be able to convert Javascript to the other syntax for editing, then back to Javascript when saved. This would allow seamless use of this tool while making the code accessible to the entire vanilla JS community. I envision this integrated into editors like Sublime Text. Alternatively it could be a grunt task. A challenge will be editing a js file while preserving existing coding conventions and unedited portions as-is. I also have no experience with compilers, parsers, etc although I have an interest.
Unlike other transpilers, it is meant to be read in from vanilla js and output code that is indistinguishable from hand-written js. This would allow you to use the cleaner syntax while working on any vanilla js and it would work when contributing to existing vanilla js open source libraries.
Would this be useful?