function isUndefined(v) {
    var undef;
    return v===undef;
}

function rawPopup(url, target, features) {
    if (isUndefined(target)) {
        target = '_blank';
    }

    var newWindow = window.open(url, target, features);
    newWindow.focus();
    return newWindow;
}

function linkPopup(src, features) {
    return rawPopup(src.getAttribute('href'), src.getAttribute('target') || '_blank', features);
}