gistfile1.el

(defun compile-cljs-on-after-save-hook ()
  (add-hook 'after-save-hook
            '(lambda ()
               (interactive)
               (let* ((file-name (buffer-file-name))
                      (file-name-dir (file-name-directory file-name)))
                 (if (string-match "\.cljs$" file-name)
                     (async-shell-command
                      (concat "cljsc " file-name-dir
                              ;; " '{:optimizations :advanced}' > "
                              ;; file-name-dir "compiled.js"
                              ) nil nil))))))
(add-hook 'clojure-mode-hook 'compile-cljs-on-after-save-hook)
(setq auto-mode-alist (cons '("\\.cljs$" . clojure-mode) auto-mode-alist))