Merge pull request #379 from Esri/doc/jsapi-to-rest-js

docs: demo how to retrieve credentials from the jsapi too

demos/jsapi-integration/README.md

@@ -1,8 +1,25 @@
 # Passing authentication to the JSAPI
 
-This demo shows how to use `arcgis-rest-js` with  the ArcGIS API for JavaScript. A typical use case would be when you need to query items or feature data _before_ you are ready to display a map or scene view. In this scenario, you should load the light-weight `arcgis-rest-js` libraries first and use them to perform your queries and/or authenticate with the ArcGIS platform. Then when you are ready to show a map or scene view, you would lazy-load the ArcGIS API for JavaScript with something like [esri-loader](https://github.com/Esri/esri-loader) and use it to create the map. 
+This demo shows how to use `arcgis-rest-js` with  the ArcGIS API for JavaScript. A typical use case would be when you need to query items or feature data _before_ you are ready to display a map or scene view. In this scenario, you should load the light-weight `arcgis-rest-js` libraries first and use them to perform your queries and/or authenticate with the ArcGIS platform. Then when you are ready to show a map or scene view, you would lazy-load the ArcGIS API for JavaScript with something like [esri-loader](https://github.com/Esri/esri-loader) and use it to create the map.
 
 ## Running this demo
 1. Run `npm run bootstrap` in the repository's root directory.
 1. Run `npm start` to spin up the development server.
 1. Visit [http://localhost:8080](http://localhost:8080).
+
+```js
+// from rest-js
+const session = new UserSession(/* */);
+
+// session wont fetch a token until a request is a made
+session.getToken("https://www.arcgis.com/sharing/rest")
+  .then(() => {
+    esriId.registerToken(session.toCredential()); // JSAPI Identity Manager
+  })
+
+// from jsapi
+esriId.getCredential("https://www.arcgis.com/sharing/rest")
+  .then(cred => {
+    const session = new UserSession.fromCredential(cred);
+  })
+```

demos/jsapi-integration/index.html

@@ -72,6 +72,12 @@
               map: webmap,
               container: "viewDiv"
             });
+
+            // you can also pass credentials in the other direction
+            esriId.getCredential("https://arcgis.com/sharing/rest/")
+              .then(cred => {
+                const session2 = new arcgisRest.UserSession.fromCredential(cred);
+              })
           });
       });
     </script>