rsjx mode with attempt at auto-detecting JSX files

lang-web.el

(use-package rjsx-mode
  :mode "\\.jsx$"
  :mode "components/.+\\.js$"
  :init
  ;; auto-detect JSX file
  ;; https://github.com/shahinism/emacs.d/blob/master/configs.org
  ;; source: https://github.com/hlissner/.emacs.d/blob/master/modules/lang/javascript/config.el
  (push (cons (lambda ()
                (and buffer-file-name
                     (equal (file-name-extension buffer-file-name) "js")
                     (re-search-forward "\\(^\\s-*import React\\|\\( from \\|require(\\)[\"']react\\)"
                                        magic-mode-regexp-match-limit t)
                     (progn
                       (goto-char (match-beginning 1))
                       ;; sp-point-in-string-or-comment requires smartparens package
                       (not (sp-point-in-string-or-comment)))))
              'rjsx-mode)
        magic-mode-alist)
  :config
  ;; match gatsby.js layout
  (add-to-list 'auto-mode-alist '("components\\/.*\\.js\\'" . rjsx-mode))
  (add-to-list 'auto-mode-alist '("layouts\\/.*\\.js\\'" . rjsx-mode))
  (add-to-list 'auto-mode-alist '("templates\\/.*\\.js\\'" . rjsx-mode))
  (add-to-list 'auto-mode-alist '("pages\\/.*\\.js\\'" . rjsx-mode)))