Sample of using Tiled WMS overlay with ArcGIS JavaScript API 3.9.
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<html>
<head>
<title>Tiled WMS overlay</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1, user-scalable=no">
<link rel="stylesheet" href="https://js.arcgis.com/3.9/js/esri/css/esri.css">
<link rel="stylesheet" href="css/app.css">
<style>
html, body {
height: 100%;
padding: 0;
margin: 0;
background: rgb(14, 21, 30);
height: 100%;
}
#map {
position: absolute;
height: 100%;
width: 100%;
background-color: #333;
}
</style>
</head>
<body>
<div id="map"></div>
<script src="https://js.arcgis.com/3.9/"></script>
<script src="globalMercator.js"></script>
<script src="app.js"></script>
</body>
</html>
Modified http://js.arcgis.com/3.9/ to a secure url
https://js.arcgis.com/3.9/