Regex find links, og undgå eksisterende

JScript kode 

 function tokenize(text) {
     var Token = function(text) {
         this.text = text;
     };
     Token.prototype.isTag = function() {
         return this.text.charAt(0) === '<';
     };
     
     Token.prototype.isStartTag = function() {
         return this.isTag() && this.text.charAt(1) !== '/';
     };
     
     Token.prototype.isEndTag = function() {
         return this.isTag() && this.isStartTag() === false;
     };
     
     Token.prototype.getTagName = function() {
         return this.text.replace(/^<\/?([a-zA-Z]+).*$/, '$1').toLowerCase();
     };
 
     var tokens = [],
         idx = 0,
         c;
     for (var i = 0; i < text.length; i++) {
         c = text.charAt(i);
         if (c === '<') {
             if (idx !== i) {
                 tokens.push(new Token(text.substring(idx, i)));
             }
             idx = i;
         } else if (c === '>') {
             tokens.push(new Token(text.substring(idx, i + 1)));
             idx = i + 1;
         }
     }
     
     if (idx < text.length - 1) {
         tokens.push(new Token(text.substring(idx, text.length)));
     }
     
     return tokens;
 };
 
 function substituteLinks (text) {
     var identifier = '[a-zA-Z0-9_+]+',
         protocol = '((https?)|(ftp)|(mailto))',
         username_and_optional_password = '(' + identifier + '(:' + identifier + ')?@)?',
         ip_address = '\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}',
         hostname = '[a-zA-Z0-9_\.]+',
         host = '((' + ip_address + ')|(' + hostname + '))',
         port = '(:[0-9]+)?',
         host_and_port = '(' + host + port + ')',
         key_with_optional_value = identifier + '(=(' + identifier + ')?)?',
         path = '[/a-zA-Z0-9_+\\&;\\.\\-]+',
         query = '(\\?(' + key_with_optional_value + '(&' + key_with_optional_value + ')*' + ')?)?',
         anchor = '(#' + identifier + ')?',
         url = '(' + protocol + '://' + username_and_optional_password + host_and_port + path + query + anchor + ')',
         regex = new RegExp(url, 'g');
 
     return text.replace(regex, '<a href="$1">$1</a>');
 };
 
 function createLinks(text) {
 
     var tokens = tokenize(text),
         t,
         anchorNesting = 0,
         html = '';
 
     for (var i = 0; i < tokens.length; i++) {
         t = tokens[i];
         if (t.isStartTag() && t.getTagName() === 'a') {
             anchorNesting++;
         } else if (t.isEndTag() && t.getTagName() === 'a') {
             anchorNesting--;
         } else if (t.isTag() === false && anchorNesting === 0) {
             t.text = substituteLinks(t.text);
         }
         html += t.text;
     }
     return html;
 }

JScript kode 

 url = '((' + protocol + '://)?' + username_and_optional_password + host_and_port + path + query + anchor + ')',