This function is for evil-mode Emacs users. It executes the passed callback when 'fd' sequence is quickly pressed.

evil-fd-trigger.el

;; inspired from:
;; https://github.com/roman/emacs.d/blob/master/zoo/zoo-evil.el
(evil-define-command fd-trigger (callback)
  "Allows to execute the passed function using 'fd'."
  :repeat change
  (let ((modified (buffer-modified-p)))
    (insert "f")
    (let ((evt (read-event
                (format "Insert %c to exit insert state" ?d)
                nil 0.2)))
      (cond
       ((null evt)
          (message ""))
       ((and (integerp evt)
             (char-equal evt ?d))
          ;; remove the f character
          (delete-char -1)
          (set-buffer-modified-p modified)
          (funcall callback))
       (t ; otherwise
          (setq unread-command-events (append unread-command-events
                                              (list evt))))))))