Emacs mode to edit JSON
js-mode supports syntax highlighting and indentation for json files.
This is as of Emacs 23.2, when espresso-mode was incorporated into Emacs and renamed js-mode.
Check it out: http://www.nongnu.org/espresso/
Have you tried Steve Yegge's js2-mode for Emacs?
If you want something lightweight try this major-mode I hacked together: https://github.com/joshwnj/json-mode
It's actually no more than some extra syntax highlighting on top of javascript-mode, but for my purposes I've found it to work quite well.
Another common use-case is auto-formatting a JSON file (eg. if it's whitespace-compressed and you want more readability). To do this I'm just piping the buffer through a command-line script: C-u M-|
+1 for Josh's json-mode -- works well for me. I added
(defun beautify-json ()
(interactive)
(let ((b (if mark-active (min (point) (mark)) (point-min)))
(e (if mark-active (max (point) (mark)) (point-max))))
(shell-command-on-region b e
"python -m json.tool" (current-buffer) t)))
and
(define-key json-mode-map (kbd "C-c C-f") 'beautify-json)
to json-mode.el to make the shell command invocation easier.
UPDATE: For those of you with a need/desire to do this with unicode, see my question here. The upshot is rather than using:
python -m json.tool
you will want to use
python -c 'import sys,json; data=json.loads(sys.stdin.read()); print json.dumps(data,sort_keys=True,indent=4).decode("unicode_escape").encode("utf8","replace")'
This both beautifies the JSON as well as preserving the original Unicode content.