javascript function lookup

javascript-imenu.el

(defun es-js-imenu-create-index ()
  "Return an imenu index for the current buffer."
  (save-excursion
    (save-restriction
      (let (unique-names result name pos)
        (widen)
        (goto-char (point-min))
        (while (re-search-forward
                (concat "\\(\\_<.+?\\_>\\) = function"
                        "\\|"
                        "\\(\\_<.+?\\_>\\): function"
                        "\\|"
                        "function \\(\\_<.+?\\_>\\)")
                nil t)
          (setq name (or (match-string-no-properties 1)
                         (match-string-no-properties 2)
                         (match-string-no-properties 3))
                pos (or (match-beginning 1)
                        (match-beginning 2)
                        (match-beginning 3)))
          (when (member name unique-names)
            (let ((counter 2)
                  new-name)
              (while (progn (setq new-name (concat name "[" (int-to-string counter) "]"))
                            (member new-name unique-names))
                (incf counter))
              (setq name new-name)))
          (push name unique-names)
          (push (cons name (js--maybe-make-marker pos)) result))
        (nreverse result)))))


(defun* es-js-imenu-goto-function-at-point ()
  (interactive)
  (let* (( word (or (thing-at-point 'symbol)
                    (return-from es-js-imenu-goto-function-at-point)))
         ( index (es-js-imenu-create-index))
         ( pair (or (find-if (lambda (cons)
                               (and (string-prefix-p word (car cons))
                                    (not (= (point) (marker-position (cdr cons))))))
                             index)
                    (return-from es-js-imenu-goto-function-at-point))))
    (ring-insert find-tag-marker-ring (point-marker))
    (goto-char (marker-position (cdr pair))))
  )

(add-hook 
 'js-mode-hook
 (lambda ()
   (define-key 'js-mode-map (kbd "M-.") 'es-js-imenu-goto-function-at-point)
   (setq-local imenu-create-index-function 'es-js-imenu-create-index)))