third application :Directions widget

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
    <title>Directions Widget</title>
    <link rel="stylesheet" href="http://js.arcgis.com/3.13/dijit/themes/claro/claro.css">
    <link rel="stylesheet" href="http://js.arcgis.com/3.13/esri/css/esri.css">
    <style>
      html, body, #map {
        height:100%;
        width:100%;
        margin:0;
        padding:0;
      }
      body {
        background-color:#FFF;
        overflow:hidden;
        font-family:"Trebuchet MS";
      }
    </style>

    <script src="http://js.arcgis.com/3.13/"></script>
    <script>
      require([
        "esri/map", "esri/dijit/Directions", 
        "dojo/parser", 
        "dijit/layout/BorderContainer", "dijit/layout/ContentPane", "dojo/domReady!"
      ], function(
        Map, Directions,parser
      ) {
        parser.parse();
        

        var map = new Map("map", {
          basemap: "streets",
          center:[-98.56,39.82],
          zoom: 4
        });

        var directions = new Directions({
          map: map,
          routeTaskUrl: "http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Network/USA/NAServer/Route",
        },"dir");
        directions.startup();
      });
    </script>
  </head>
  <body class="claro">
    <div data-dojo-type="dijit/layout/BorderContainer" 
         data-dojo-props="design:'headline', gutters:false" 
         style="width:100%;height:100%;">
      <div data-dojo-type="dijit/layout/ContentPane" 
           data-dojo-props="region:'right'" 
           style="width:300px;height:600px;">
        
        <div id="dir"></div>
      </div>
      <div id="map" 
           data-dojo-type="dijit/layout/ContentPane" 
           data-dojo-props="region:'center'">
      </div>
    </div>
  </body>
</html>

parser.parse()：

dojo的parser会把html节点根据所声明的类型（data-dojo-type）转化为相应的dijit组件的template（dojo类型的节点），并且会给这些相应的template赋上对应的id，属性等等，并且把组件的id注册到dijit.registry里。在注册到registry的过程中，如果没有显式的指定id，则registry会生成一个自增的id赋值给相应的组件，如果显式的指定id，则使用指定的id。如果对同一节点多次parse操作，并且这些节点中有指定id的情况，就会出现你说的这种情况，报的错应该是Tried to register widget with id==xxx but that id is already registered。如果想分步加载并且多次parse，可以加载一个节点parse一个节点。或者在代码中调用dijit组件的startup方法也可实现parse的同样效果。


startup（）：