https://panic.com/coda/ - This looks like it will do the job.
Edit: Just saw that coda might cost money to use, so here's another you can try: https://macromates.com/download
Hopefully one of them has a "free for personal use" thing going on. - I'm surprised to see sites offering licenses for text editors.
Edit 2: I found a really good online tool that parses json very nicely: http://www.jsoneditoronline.org/

Again, info provided as-is ;-)