Unescape even fairly mutilated escaped string in Javascript

StringUnescaper.coffee

String::unescape = (strict = false) ->
  ###
  # Take escaped text, and return the unescaped version
  #
  # @param string str | String to be used
  # @param bool strict | Stict mode will remove all HTML
  #
  # Test it here:
  # https://jsfiddle.net/tigerhawkvok/t9pn1dn5/
  #
  # Code: https://gist.github.com/tigerhawkvok/285b8631ed6ebef4446d
  ###
  # Create a dummy element
  element = document.createElement("div")
  decodeHTMLEntities = (str) ->
    if str? and typeof str is "string"
      unless strict is true
        # escape HTML tags
        str = escape(str).replace(/%26/g,'&').replace(/%23/g,'#').replace(/%3B/g,';')
      else
        str = str.replace(/<script[^>]*>([\S\s]*?)<\/script>/gmi, '')
        str = str.replace(/<\/?\w(?:[^"'>]|"[^"]*"|'[^']*')*>/gmi, '')
      element.innerHTML = str
      if element.innerText
        # Do we support innerText?
        str = element.innerText
        element.innerText = ""
      else
        # Firefox
        str = element.textContent
        element.textContent = ""
    unescape(str)
  # Remove encoded or double-encoded tags
  fixHtmlEncodings = (string) ->
    string = string.replace(/\&amp;#/mg, '&#') # The rest, for double-encodings
    string = string.replace(/\&quot;/mg, '"')
    string = string.replace(/\&quote;/mg, '"')
    string = string.replace(/\&#95;/mg, '_')
    string = string.replace(/\&#39;/mg, "'")
    string = string.replace(/\&#34;/mg, '"')
    string = string.replace(/\&#62;/mg, '>')
    string = string.replace(/\&#60;/mg, '<')
    string
  # Run it
  tmp = fixHtmlEncodings(this)
  decodeHTMLEntities(tmp)

StringUnescaper.js

String.prototype.unescape = function(strict) {
  var decodeHTMLEntities, element, fixHtmlEncodings, tmp;
  if (strict == null) {
    strict = false;
  }

  /*
   * Take escaped text, and return the unescaped version
   *
   * @param string str | String to be used
   * @param bool strict | Stict mode will remove all HTML
   *
   * Test it here:
   * https://jsfiddle.net/tigerhawkvok/t9pn1dn5/
   *
   * Code: https://gist.github.com/tigerhawkvok/285b8631ed6ebef4446d
   */
  element = document.createElement("div");
  decodeHTMLEntities = function(str) {
    if ((str != null) && typeof str === "string") {
      if (strict !== true) {
        str = escape(str).replace(/%26/g, '&').replace(/%23/g, '#').replace(/%3B/g, ';');
      } else {
        str = str.replace(/<script[^>]*>([\S\s]*?)<\/script>/gmi, '');
        str = str.replace(/<\/?\w(?:[^"'>]|"[^"]*"|'[^']*')*>/gmi, '');
      }
      element.innerHTML = str;
      if (element.innerText) {
        str = element.innerText;
        element.innerText = "";
      } else {
        str = element.textContent;
        element.textContent = "";
      }
    }
    return unescape(str);
  };
  fixHtmlEncodings = function(string) {
    string = string.replace(/\&amp;#/mg, '&#');
    string = string.replace(/\&quot;/mg, '"');
    string = string.replace(/\&quote;/mg, '"');
    string = string.replace(/\&#95;/mg, '_');
    string = string.replace(/\&#39;/mg, "'");
    string = string.replace(/\&#34;/mg, '"');
    string = string.replace(/\&#62;/mg, '>');
    string = string.replace(/\&#60;/mg, '<');
    return string;
  };
  tmp = fixHtmlEncodings(this);
  return decodeHTMLEntities(tmp);
};