Elisp: Replace HTML Entities

By Xah Lee. Date: . Last updated: .

Here's commands to replace HTML entities to character or reverse.

Escape HTML Chars to Entities

Here's a command to replace < > & to entities &lt; &gt; &amp; or reverse.

(defun xah-html-escape-char-to-entity (@begin @end &optional @entity-to-char-p)
  "Replace HTML chars & < > to HTML entities on current text block or selection.
The string replaced are:
 & ⇒ &amp;
 < ⇒ &lt;
 > ⇒ &gt;

Highlight changed places.
If `universal-argument' is called first, the replacement direction is reversed.

When called in lisp code, @begin @end are region begin/end positions. If @entity-to-char-p is true, reverse change direction.

URL `http://ergoemacs.org/emacs/elisp_replace_html_entities_command.html'
Version 2020-08-30"
  (interactive
   (save-excursion
     (list
      (if (use-region-p)
          (region-beginning)
        (progn
          (re-search-backward "\n[ \t]*\n" nil "move")
          (re-search-forward "\n[ \t]*\n" nil "move")
          (point)))
      (if (use-region-p)
          (region-end)
        (progn
          (re-search-forward "\n[ \t]*\n" nil "move")
          (re-search-backward "\n[ \t]*\n" nil "move")
          (point)))
      (if current-prefix-arg t nil))))
  (let (($changedItems '())
        ($findReplaceMap
         (if @entity-to-char-p
             ;; this to prevent creating a replacement sequence out of blue
             [
              ["&amp;" "螽⛫1"] ["&lt;" "螽⛫2"] ["&gt;" "螽⛫3"]
              ["螽⛫1" "&"] ["螽⛫2" "<"] ["螽⛫3" ">"]
              ]
           [ ["&" "&amp;"] ["<" "&lt;"] [">" "&gt;"] ]
           )))
    (save-excursion
      (save-restriction
        (narrow-to-region @begin @end)
        (let ( (case-fold-search nil))
          (mapc
           (lambda ($x)
             (goto-char (point-min))
             (while (search-forward (elt $x 0) nil t)
               (push (format "%s %s" (point) $x) $changedItems)
               (replace-match (elt $x 1) "FIXEDCASE" "LITERAL")
               (overlay-put (make-overlay (- (point) (length (elt $x 1))) (point)) 'font-lock-face '(:foreground "red"))))
           $findReplaceMap))))))

Named Entities to Unicode

Replace HTML named entities such as &eacute; to its Unicode character é.

(defun xah-html-named-entity-to-char (@begin @end)
  "Replace HTML named entity to Unicode character in current text block or selection.
Changed places are highlighted.
For example, “&copy;” becomes “©”.
The following HTML Entities are not replaced: &amp; &lt; &gt;

When called in lisp code, @begin @end are region begin/end positions.

URL `http://ergoemacs.org/emacs/elisp_replace_html_entities_command.html'
Version 2020-08-30"
  (interactive
   (if (use-region-p)
       (list (region-beginning) (region-end))
     (save-excursion
       (list
        (progn
          (search-backward "\n\n" nil "NOERROR" )
          (search-forward "\n\n" nil "NOERROR")
          (point))
        (progn
          (search-forward "\n\n" nil "NOERROR")
          (search-backward "\n\n" nil "NOERROR" )
          (point))))))
  (let (
        ($replaceMap
         [
          ["&nbsp;" " "] ["&ensp;" " "] ["&emsp;" " "] ["&thinsp;" " "]
          ["&rlm;" "‏"] ["&lrm;" "‎"] ["&zwj;" "‍"] ["&zwnj;" "‌"]

          ["&iexcl;" "¡"] ["&cent;" "¢"] ["&pound;" "£"] ["&curren;" "¤"] ["&yen;" "¥"]
          ["&brvbar;" "¦"] ["&sect;" "§"] ["&uml;" "¨"] ["&copy;" "©"] ["&ordf;" "ª"]
          ["&laquo;" "«"] ["&not;" "¬"] ["&shy;" "­"] ["&reg;" "®"] ["&macr;" "¯"]
          ["&deg;" "°"] ["&plusmn;" "±"] ["&sup2;" "²"] ["&sup3;" "³"] ["&acute;" "´"]
          ["&micro;" "µ"] ["&para;" "¶"] ["&middot;" "·"] ["&cedil;" "¸"] ["&sup1;" "¹"]
          ["&ordm;" "º"] ["&raquo;" "»"] ["&frac14;" "¼"] ["&frac12;" "½"]
          ["&frac34;" "¾"] ["&iquest;" "¿"]

          ["&Agrave;" "À"] ["&Aacute;" "Á"] ["&Acirc;" "Â"] ["&Atilde;" "Ã"] ["&Auml;" "Ä"]
          ["&Aring;" "Å"] ["&AElig;" "Æ"] ["&Ccedil;" "Ç"] ["&Egrave;" "È"] ["&Eacute;" "É"]
          ["&Ecirc;" "Ê"] ["&Euml;" "Ë"] ["&Igrave;" "Ì"] ["&Iacute;" "Í"] ["&Icirc;" "Î"]
          ["&Iuml;" "Ï"] ["&ETH;" "Ð"] ["&Ntilde;" "Ñ"] ["&Ograve;" "Ò"] ["&Oacute;" "Ó"]
          ["&Ocirc;" "Ô"] ["&Otilde;" "Õ"] ["&Ouml;" "Ö"] ["&times;" "×"] ["&Oslash;" "Ø"]
          ["&Ugrave;" "Ù"] ["&Uacute;" "Ú"] ["&Ucirc;" "Û"] ["&Uuml;" "Ü"] ["&Yacute;" "Ý"]
          ["&THORN;" "Þ"] ["&szlig;" "ß"] ["&agrave;" "à"] ["&aacute;" "á"] ["&acirc;" "â"]
          ["&atilde;" "ã"] ["&auml;" "ä"] ["&aring;" "å"] ["&aelig;" "æ"] ["&ccedil;" "ç"]
          ["&egrave;" "è"] ["&eacute;" "é"] ["&ecirc;" "ê"] ["&euml;" "ë"] ["&igrave;" "ì"]
          ["&iacute;" "í"] ["&icirc;" "î"] ["&iuml;" "ï"] ["&eth;" "ð"] ["&ntilde;" "ñ"]
          ["&ograve;" "ò"] ["&oacute;" "ó"] ["&ocirc;" "ô"] ["&otilde;" "õ"] ["&ouml;" "ö"]

          ["&divide;" "÷"] ["&oslash;" "ø"] ["&ugrave;" "ù"] ["&uacute;" "ú"] ["&ucirc;" "û"]
          ["&uuml;" "ü"] ["&yacute;" "ý"] ["&thorn;" "þ"] ["&yuml;" "ÿ"] ["&fnof;" "ƒ"]

          ["&Alpha;" "Α"] ["&Beta;" "Β"] ["&Gamma;" "Γ"] ["&Delta;" "Δ"] ["&Epsilon;" "Ε"]
          ["&Zeta;" "Ζ"] ["&Eta;" "Η"] ["&Theta;" "Θ"] ["&Iota;" "Ι"] ["&Kappa;" "Κ"]
          ["&Lambda;" "Λ"] ["&Mu;" "Μ"] ["&Nu;" "Ν"] ["&Xi;" "Ξ"] ["&Omicron;" "Ο"]
          ["&Pi;" "Π"] ["&Rho;" "Ρ"] ["&Sigma;" "Σ"] ["&Tau;" "Τ"] ["&Upsilon;" "Υ"]
          ["&Phi;" "Φ"] ["&Chi;" "Χ"] ["&Psi;" "Ψ"] ["&Omega;" "Ω"] ["&alpha;" "α"]
          ["&beta;" "β"] ["&gamma;" "γ"] ["&delta;" "δ"] ["&epsilon;" "ε"] ["&zeta;" "ζ"]
          ["&eta;" "η"] ["&theta;" "θ"] ["&iota;" "ι"] ["&kappa;" "κ"] ["&lambda;" "λ"]
          ["&mu;" "μ"] ["&nu;" "ν"] ["&xi;" "ξ"] ["&omicron;" "ο"] ["&pi;" "π"]
          ["&rho;" "ρ"] ["&sigmaf;" "ς"] ["&sigma;" "σ"] ["&tau;" "τ"] ["&upsilon;" "υ"]
          ["&phi;" "φ"] ["&chi;" "χ"] ["&psi;" "ψ"] ["&omega;" "ω"] ["&thetasym;" "ϑ"]
          ["&upsih;" "ϒ"] ["&piv;" "ϖ"]

          ["&bull;" "•"] ["&hellip;" "…"] ["&prime;" "′"] ["&Prime;" "″"] ["&oline;" "‾"]
          ["&frasl;" "⁄"] ["&weierp;" "℘"] ["&image;" "ℑ"] ["&real;" "ℜ"] ["&trade;" "™"]
          ["&alefsym;" "ℵ"] ["&larr;" "←"] ["&uarr;" "↑"] ["&rarr;" "→"] ["&darr;" "↓"]
          ["&harr;" "↔"] ["&crarr;" "↵"] ["&lArr;" "⇐"] ["&uArr;" "⇑"] ["&rArr;" "⇒"]
          ["&dArr;" "⇓"] ["&hArr;" "⇔"] ["&forall;" "∀"] ["&part;" "∂"] ["&exist;" "∃"]
          ["&empty;" "∅"] ["&nabla;" "∇"] ["&isin;" "∈"] ["&notin;" "∉"] ["&ni;" "∋"]
          ["&prod;" "∏"] ["&sum;" "∑"] ["&minus;" "−"] ["&lowast;" "∗"] ["&radic;" "√"]
          ["&prop;" "∝"] ["&infin;" "∞"] ["&ang;" "∠"] ["&and;" "∧"] ["&or;" "∨"]
          ["&cap;" "∩"] ["&cup;" "∪"] ["&int;" "∫"] ["&there4;" "∴"] ["&sim;" "∼"]
          ["&cong;" "≅"] ["&asymp;" "≈"] ["&ne;" "≠"] ["&equiv;" "≡"] ["&le;" "≤"]
          ["&ge;" "≥"] ["&sub;" "⊂"] ["&sup;" "⊃"] ["&nsub;" "⊄"] ["&sube;" "⊆"]
          ["&supe;" "⊇"] ["&oplus;" "⊕"] ["&otimes;" "⊗"] ["&perp;" "⊥"] ["&sdot;" "⋅"]
          ["&lceil;" "⌈"] ["&rceil;" "⌉"] ["&lfloor;" "⌊"] ["&rfloor;" "⌋"] ["&lang;" "〈"]
          ["&rang;" "〉"] ["&loz;" "◊"] ["&spades;" "♠"] ["&clubs;" "♣"] ["&hearts;" "♥"]
          ["&diams;" "♦"] ["&quot;" "\""] ["&OElig;" "Œ"] ["&oelig;" "œ"] ["&Scaron;" "Š"]
          ["&scaron;" "š"] ["&Yuml;" "Ÿ"] ["&circ;" "ˆ"] ["&tilde;" "˜"] ["&ndash;" "–"]
          ["&mdash;" "—"] ["&lsquo;" "‘"] ["&rsquo;" "’"] ["&sbquo;" "‚"] ["&ldquo;" "“"]
          ["&rdquo;" "”"] ["&bdquo;" "„"] ["&dagger;" "†"] ["&Dagger;" "‡"] ["&permil;" "‰"]
          ["&lsaquo;" "‹"] ["&rsaquo;" "›"] ["&euro;" "€"]
          ]))
    (save-restriction
      (narrow-to-region @begin @end)
      (let ( (case-fold-search nil))
        (mapc
         (lambda ($x)
           (goto-char (point-min))
           (while (search-forward (elt $x 0) nil t)
             (replace-match (elt $x 1))
             (overlay-put (make-overlay (- (point) (length (elt $x 1))) (point)) 'font-lock-face '(:foreground "red"))))
         $replaceMap)))))

Escape HTML Chars to Unicode

Sometimes it's useful to convert the HTML entities to special unicode chars, to avoid the whole encoding/decoding/entities complexity.

(defun xah-html-escape-char-to-unicode (@begin @end &optional @fullwidth-to-ascii-p)
  "Replace chars < > & to fullwidth version < > & in current text block or selection.

Highlight changed places.
If `universal-argument' is called first, the replacement direction is reversed.

When called in lisp code, @begin @end are region begin/end positions. If @fullwidth-to-ascii-p is true, reverse change direction.

URL `http://ergoemacs.org/emacs/elisp_replace_html_entities_command.html'
Version 2020-08-30"
  (interactive
   (list
    (if (use-region-p)
        (region-beginning)
      (progn
        (re-search-backward "\n[ \t]*\n" nil "move")
        (re-search-forward "\n[ \t]*\n" nil "move")
        (point)))
    (if (use-region-p)
        (region-end)
      (progn
        (re-search-forward "\n[ \t]*\n" nil "move")
        (re-search-backward "\n[ \t]*\n" nil "move")
        (point)))
    (if current-prefix-arg t nil)))
  (let (($findReplaceMap
         (if @fullwidth-to-ascii-p
             [ ["&" "&"] [ "<" "<"] [ ">" ">"] ]
           [ ["&" "&"] ["<" "<"] [">" ">"] ]
           )))
    (save-excursion
      (save-restriction
        (narrow-to-region @begin @end)
        (mapc
         (lambda ($x)
           (goto-char (point-min))
           (while (search-forward (elt $x 0) nil t)
             (replace-match (elt $x 1))
             (overlay-put (make-overlay (- (point) (length (elt $x 1))) (point)) 'font-lock-face '(:foreground "red"))))
         $findReplaceMap)))))

HTML

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