jQuery Ajax Loading

HTML

<script src="https://www.w3schools.com/jquery/demo_wait.gif"></script>
<script src="https://www.w3schools.com/jquery/demo_ajax_load.asp"></script>
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $(document).ajaxStart(function(){
        $("#wait").css("display", "block");
    });
    $(document).ajaxComplete(function(){
        $("#wait").css("display", "none");
    });
    $("button").click(function(){
        $("#txt").load("https://www.w3schools.com/jquery/demo_ajax_load.asp");
    });
});
</script>
</head>
<body>

<div id="txt"><h2>Let AJAX change this text</h2></div>

<button>Change Content</button>

<div id="wait" style="display:none;width:69px;height:89px;border:1px solid black;position:absolute;top:50%;left:50%;padding:2px;"><img src='https://www.w3schools.com/jquery/demo_wait.gif' width="64" height="64" /><br>Loading..</div>

</body>
</html>