ltx/src/escape.js

<xml for="JavaScript">

const escapeXMLTable = {
  "&": "&",
  "<": "&lt;",
  ">": "&gt;",
  '"': "&quot;",
  "'": "&apos;",
};

function escapeXMLReplace(match) {
  return escapeXMLTable[match];
}

const unescapeXMLTable = {
  "&amp;": "&",
  "&lt;": "<",
  "&gt;": ">",
  "&quot;": '"',
  "&apos;": "'",
};

function unescapeXMLReplace(match) {
  if (match[1] === "#") {
    const num =
      match[2] === "x"
        ? parseInt(match.slice(3), 16)
        : parseInt(match.slice(2), 10);
    // https://www.w3.org/TR/xml/#NT-Char defines legal XML characters:
    // #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]
    if (
      num === 0x9 ||
      num === 0xa ||
      num === 0xd ||
      (num >= 0x20 && num <= 0xd7ff) ||
      (num >= 0xe000 && num <= 0xfffd) ||
      (num >= 0x10000 && num <= 0x10ffff)
    ) {
      return String.fromCodePoint(num);
    }
    throw new Error("Illegal XML character 0x" + num.toString(16));
  }
  if (unescapeXMLTable[match]) {
    return unescapeXMLTable[match] || match;
  }
  throw new Error("Illegal XML entity " + match);
}

export function escapeXML(s) {
  return s.replace(/["&'<>]/g, escapeXMLReplace);
}

export function unescapeXML(s) {
  let result = "";
  let start = -1;
  let end = -1;
  let previous = 0;
  while (
    (start = s.indexOf("&", previous)) !== -1 &&
    (end = s.indexOf(";", start + 1)) !== -1
  ) {
    result =
      result +
      s.slice(previous, start) +
      unescapeXMLReplace(s.slice(start, end + 1));
    previous = end + 1;
  }

  // shortcut if loop never entered:
  // return the original string without creating new objects
  if (previous === 0) return s;

  // push the remaining characters
  result = result + s.substring(previous);

  return result;
}

export function escapeXMLText(s) {
  return s.replace(/[&<>]/g, escapeXMLReplace);
}

export function unescapeXMLText(s) {
  return s.replace(/&(amp|#38|lt|#60|gt|#62);/g, unescapeXMLReplace);
}