Arcgis api for javascript学习笔记(3.2X版本)-Map图层叠加以及基本操作

1. 不设置默认底图，第一个图层作为底图，然后叠加另外一个图层

先添加图层1，第一个图层1作为默认底图，然后在图层1上叠加图层2，并设置图层2的透明度为50%。

 <!DOCTYPE html>
 <html>
 <head>
     <title>simple demo</title>
     <link rel="stylesheet" href="http://localhost:8003/arcgis_js_v320_api/library/3.20/3.20/esri/css/esri.css">
     <style type="text/css">
         html, body { margin: 0; padding: 0; height: 100%; width: 100%; }
         #viewDiv { width: 100%; height: 100%; }
     </style>
 </head>
 <body>
     <div id="viewDiv"></div>
     <script src="http://localhost:8003/arcgis_js_v320_api/library/3.20/3.20/init.js"></script>
     <script type="text/javascript">
         require([
             "esri/map",
             "esri/layers/ArcGISTiledMapServiceLayer",
             "dojo/domReady!"],
             function (Map, ArcGISTiledMapServiceLayer) {
                 var map = new Map("viewDiv");
                 var tms1 = new ArcGISTiledMapServiceLayer("http://cache1.arcgisonline.cn/arcgis/rest/services/ChinaOnlineCommunity/MapServer"); //图层1
                 map.addLayer(tms1);
                 var tms2 = new ArcGISTiledMapServiceLayer("http://services.arcgisonline.com/arcgis/rest/services/Demographics/USA_Projected_Population_Change/MapServer", { "opacity": 0.5 }); //图层2，透明度50%
                 map.addLayer(tms2);
             }
         );
     </script>
 </body>
 </html>

效果如下：