pp-minify-json-buffer-contents-hooks.el

;; pretty print json files when they're opened and minify them when they are saved

(add-to-list 'auto-mode-alist
             '("\\.json\\'" . (lambda ()
				(json-mode)
                                (json-pretty-print (point-min) (point-max))
                                (goto-char (point-min))
                                (set-buffer-modified-p nil))))

(defun minify-json-buffer-contents()
  "Minifies the buffer contents by removing whitespaces."
  (interactive)
  (delete-whitespace-rectangle (point-min) (point-max))
  (mark-whole-buffer)
  (goto-char (point-min))
  (while (search-forward "\n" nil t) (replace-match "" nil t)))

(add-hook 'json-mode-hook
          (lambda ()
            (add-hook 'before-save-hook 'minify-json-buffer-contents)))