I'm using the following code to display a "loading" overlay when navigating our web application. This works just fine in Chrome, Firefox und IE / Edge... but not in Safari. The event is triggered and the console log shows the event – but the visual change via jQuery show() has no effect.

$(document).ready(function() {
    $(window).on("beforeunload", function() {
        console.log("in beforeunload...");
        $("#overlay").show();
    });
});

Is this a known limitation in Safari (macOS) or am I missing something? Is there some workaround?