showdownjs/src/subParsers/autoLinks.js

showdown.subParser('autoLinks', function (text, options, globals) {
  'use strict';

  text = globals.converter._dispatch('autoLinks.before', text, options);

  var simpleURLRegex  = /\b(((https?|ftp|dict):\/\/|www\.)[^'">\s]+\.[^'">\s]+)(?=\s|$)(?!["<>])/gi,
      delimUrlRegex   = /<(((https?|ftp|dict):\/\/|www\.)[^'">\s]+)>/gi,
      simpleMailRegex = /(?:^|[ \n\t])([A-Za-z0-9!#$%&'*+-/=?^_`\{|}~\.]+@[-a-z0-9]+(\.[-a-z0-9]+)*\.[a-z]+)(?:$|[ \n\t])/gi,
      delimMailRegex  = /<(?:mailto:)?([-.\w]+@[-a-z0-9]+(\.[-a-z0-9]+)*\.[a-z]+)>/gi;

  text = text.replace(delimUrlRegex, '<a href=\"$1\">$1</a>');
  text = text.replace(delimMailRegex, replaceMail);
  //simpleURLRegex  = /\b(((https?|ftp|dict):\/\/|www\.)[-.+~:?#@!$&'()*,;=[\]\w]+)\b/gi,
  // Email addresses: <address@domain.foo>

  if (options.simplifiedAutoLink) {
    text = text.replace(simpleURLRegex, '<a href=\"$1\">$1</a>');
    text = text.replace(simpleMailRegex, replaceMail);
  }

  function replaceMail(wholeMatch, m1) {
    var unescapedStr = showdown.subParser('unescapeSpecialChars')(m1);
    return showdown.subParser('encodeEmailAddress')(unescapedStr);
  }

  text = globals.converter._dispatch('autoLinks.after', text, options);

  return text;
});