invalid JS code

<script>
function gtag_report_conversion(url) {
    var callback = function () {
        if (typeof(url) != 'undefined') {
        window.location = url;
    }
    };
    gtag('event', 'conversion', {
    'send_to': 'AW-840283043/8KgICOb2t3cQo-fWkAM',
    'event_callback': callback
    });
    return false;
}
$( document ).ready(function() {
    $( "form" ).submit(function() {
        gtag_report_conversion();
    });
});
</script>