Simple UTF-8 Quoted Printable decoder

utf8-quoted-printable-decode.js

/**
 * Decode a UTF-8 quoted printable string into a UTF8 string
 *
 * @param {string} str - UTF quoted printable string (ex. "=E8=97=A4=E6=A3=AE")
 */
function utf8QuotedPrintableDecode(str) {
  // Grab the ascii bytes separated by "=", trim first/last elements if empty
  var asciiHex = str.split(/=+/);
  if (asciiHex[0] === "") { asciiHex.shift(); }
  if (asciiHex[asciiHex.length - 1] === "") { asciiHex.pop(); }

  // Convert ascii hex into bytes
  var bytes = [];
  for (var i = 0; i < asciiHex.length; i++) {
    bytes.push(String.fromCharCode(parseInt(asciiHex[i], 16)));
  }

  // Return UTF8 decoded string (trick outlined @ http://ecmanaut.blogspot.co.uk/2006/07/encoding-decoding-utf8-in-javascript.html)
  var utf8String = decodeURIComponent(escape(bytes.join("")));
  return utf8String;
}