The application is a diff tool that minifies code and then beautifies the code before performing the diff operation so that code on one line can be compared to similar code on thousands of lines. Since there is a minifier and a beautifier required for the diff operation the minify and beautify operations can be used directly by changing the first set of options.
I don't know how much the following should bias any criticism, but it seems to define the relative audience. The actual application code is broken out from any single API, such as the DOM. The web UI can use the same application code as WSH from a Windows command line or with anything that uses Common.js, such as Node.js. I am not accurately tracking usage in Google Analytics to determine which API is getting the most use, but I am starting to believe this tool is getting more use in automated builds of internet networks than use from the browser.
I have gotten a lot of criticism on the color scheme, so I am currently working on a way to dynamically choose between color schemes.
The beautification looked a lot like the little I have seen of Jquery formating!
The minification was a mere 11%, something with which I can live.
The diff is of little use to me because I rarely do rewrites.
A decent bit of work, and good luck in your future.