In terms of credentials, just wanted to point out that Marijn is also the author of CodeMirror,[1] which is a wonderful in-browser code editor used by Light Table, Bitbucket, and lots of others.[2]
This tool is crowdfunded at indiegogo[2]
[2]http://www.indiegogo.com/projects/tern-intelligent-javascrip...
https://bugs.webkit.org/show_bug.cgi?id=92769
It's marked as RESOLVED FIXED, but I honestly can't tell from the comments if it was ever actually merged in.
There's also an initiative to begin using it in Firefox's built-in dev tools, still in-progress:
https://bugzilla.mozilla.org/show_bug.cgi?id=816756
(By the way, the difference in readability between the old and new Bugzilla is startling. Good job, Bugzilla team.)