How do I output an ISO 8601 formatted string in JavaScript?

Question

I have a Date object. How do I render the title portion of the following snippet?

Answer 1

function getdatetime() {
    d = new Date();
    return (1e3-~d.getUTCMonth()*10+d.toUTCString()+1e3+d/1)
        .replace(/1(..)..*?(\d+)\D+(\d+).(\S+).*(...)/,'$3-$1-$2T$4.$5Z')
        .replace(/-(\d)T/,'-0$1T');
}

I found the basics on Stack Overflow somewhere (I believe it was part of some other Stack Exchange code golfing), and I improved it so it works on Internet Explorer 10 or earlier as well. It's ugly, but it gets the job done.