<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        body{
            font-size: 13px;
        }
    </style>
    <script src="../js/jquery-3.5.1.js"></script>
    <script>
        $(function () {
            $("div").append(retHtml);
            function retHtml() {
                var str = "<b>Write Less Do More</b>";
                return str;
            }
        })
    </script>
</head>
<body>
    <div>jquery</div>
</body>
</html>