showdown/src/subParsers/encodeEmailAddress.js

/**
 * Created by Estevao on 12-01-2015.
 */


/**
 *  Input: an email address, e.g. "foo@example.com"
 *
 *  Output: the email address as a mailto link, with each character
 *    of the address encoded as either a decimal or hex entity, in
 *    the hopes of foiling most address harvesting spam bots. E.g.:
 *
 *    <a href="&#x6D;&#97;&#105;&#108;&#x74;&#111;:&#102;&#111;&#111;&#64;&#101;
 *       x&#x61;&#109;&#x70;&#108;&#x65;&#x2E;&#99;&#111;&#109;">&#102;&#111;&#111;
 *       &#64;&#101;x&#x61;&#109;&#x70;&#108;&#x65;&#x2E;&#99;&#111;&#109;</a>
 *
 *  Based on a filter by Matthew Wickline, posted to the BBEdit-Talk
 *  mailing list: <http://tinyurl.com/yu7ue>
 *
 */
showdown.subParser('encodeEmailAddress', function (addr) {
    'use strict';

    var encode = [
        function (ch) {
            return '&#' + ch.charCodeAt(0) + ';';
        },
        function (ch) {
            return '&#x' + ch.charCodeAt(0).toString(16) + ';';
        },
        function (ch) {
            return ch;
        }
    ];

    addr = 'mailto:' + addr;

    addr = addr.replace(/./g, function (ch) {
        if (ch === '@') {
            // this *must* be encoded. I insist.
            ch = encode[Math.floor(Math.random() * 2)](ch);
        } else if (ch !== ':') {
            // leave ':' alone (to spot mailto: later)
            var r = Math.random();
            // roughly 10% raw, 45% hex, 45% dec
            ch = (
                r > 0.9 ? encode[2](ch) :
                    r > 0.45 ? encode[1](ch) :
                        encode[0](ch)
            );
        }
        return ch;
    });

    addr = '<a href="' + addr + '">' + addr + '</a>';
    addr = addr.replace(/">.+:/g, '">'); // strip the mailto: from the visible part

    return addr;

});