在页面卸载中使用JQuery的Ajax请求

I'm trying to do this:

我试着这么做:

$(window).unload( function () { 

$.ajax({
    type: "POST",
    url: "https://localhost:8888/test.php?",
    data: "test",
    success: function(msg){
         alert( "Data Saved: " + msg );
    }
}); 
alert (c);
});
$(window).un