index.html

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
    <title>Synchronize SceneView and panorama api - 4.15</title>

    <link rel="stylesheet" href="https://js.arcgis.com/4.20/esri/themes/light/main.css" />
    <script src="https://js.arcgis.com/4.20/"></script>

    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/pannellum@2.5.6/build/pannellum.css" />
    <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/pannellum@2.5.6/build/pannellum.js"></script>

    <link rel="stylesheet" href="style/main.css" />
    <script type="text/javascript" src="js/main.js"></script>

</head>

<body>
    <div id="viewDiv"></div>
    <div id=bg>
        <div id="panorama"></div>
    </div>
</body>

</html>