<input onkeydown="kd(event)"/><input id="abc"/>
<script type="text/javascript">//<![CDATA[
    Event.prototype.__defineGetter__('repeat', function() {
        var b = false, e = this;
        if(e.which===window.EVENT_REPEAT) b = true;
        window.EVENT_REPEAT = e.which;
        return b;
    });
  function kd(e) {
        document.getElementById('abc').value = 'repeat is "' +e.repeat+ '"';
    }
//]]></script>