Emacs: Format HTML Code 📜

put this in your Emacs Init File:

(defun xah-html-format-buffer (&optional z-begin z-end z-indent-p)
  "Format HTML code of current buffer or selection.
Respect `narrow-to-region'.
if `universal-argument' is called first, format with indent (z-indent-p is true).
This command requires external command deno version 2.0.0 (released 2024-10-09).

URL `http://xahlee.info/emacs/emacs/emacs_format_html_code.html'
Created: 2024-12-23
Version: 2026-04-23"
  (interactive
   (let (xbeg xend)
     (setq xbeg (if (region-active-p) (region-beginning) (point-min)))
     (setq xend (if (region-active-p) (region-end) (point-max)))
     (list xbeg xend current-prefix-arg)))
  (let (xbeg xend)
    (progn (setq xbeg (if z-begin z-begin (if (region-active-p) (region-beginning) (point-min))))
           (setq xend (if z-end z-end (if (region-active-p) (region-end) (point-max)))))
    (let ((xpos (point))
          (xoutbuf (get-buffer-create "*xah-html-format output*"))
          xexitstatus)
      (with-current-buffer xoutbuf (erase-buffer))
      (setq xexitstatus
            (call-process-region xbeg xend "deno" nil xoutbuf nil "fmt" "-" "-q" "--ext" "html" "--indent-width" "1" "--line-width" "10000"))
      (if (eq 0 xexitstatus)
          (progn
            (delete-region xbeg xend)
            (insert-buffer-substring xoutbuf)
            (when (not z-indent-p) (xah-html-remove-indent))
            (goto-char xpos)
            (kill-buffer xoutbuf))
        (progn
          (display-buffer xoutbuf)
          (error "error xah-html-format-buffer"))))))

(defun xah-html-remove-indent ()
  "
URL `http://xahlee.info/emacs/emacs/emacs_format_html_code.html'
Created: 2025-10-23
Version: 2026-04-23"
  (interactive)
  (goto-char (point-min))
  (while (re-search-forward "\n +<\\(/?[A-Za-z]+\\)" nil t)
    (replace-match "\n<\\1" t))
  (goto-char (point-min))
  (while (re-search-forward ">\n +" nil t)
    (replace-match ">\n" t))
  (goto-char (point-min))
  (while (re-search-forward "</section>" nil t)
    (replace-match "\n</section>" t))
  (goto-char (point-min))
  (while (re-search-forward "</main>" nil t)
    (replace-match "\n</main>" t)))

part of Emacs: Xah JS Mode (JavaScript) 📦