animate.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            background: green;
            width: 100px;
            height: 100px;
            position: absolute;
            margin: 0;
            padding: 0;
            }
    </style>
</head>
<body>
    <div class="box"></div>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

    <script>
        function animasi() {
            $(".box").animate({
                left: "+=300",
                opacity: "0.5"
            }, 1000, callback);
        }

        function callback() {
            $(this).animate({
                opacity: "1",
                left: "-=300"
            }, 1000, animasi);
        }

        $(document).ready(() => {
            animasi();
        })
    </script>
</body>
</html>