pentadactyl - get ip address function

gistfile1.js

    function ip() {
        var req = new XMLHttpRequest();
        req.open('GET', 'http://checkip.dyndns.org/', true);

        req.onreadystatechange = function (ev) {
            if (req.readyState == 4) {
                var ip_re = /[0-9]+.[0-9]+.[0-9]+.[0-9]+/g;
                try {
                    dactyl.echo(req.responseText.match(ip_re)[0]);
                }
                catch (err) {
                    dactyl.echo(err);
                }
            }
        }
        req.send(null);
    }

/* 
 * map in pentadactyl with:
 *   command ip -js ip()
 *
 */