lab.md

###Add a vector tile layer

In this lab you will add a vector tile layer to an ArcGIS API for JavaScript application.

1. Click create_starter_map/index.html and copy the contents to a new jsbin.com.

2. Update the require statement and function definition:

require([
  "esri/Map",
  "esri/views/MapView",
  /*** ADD ***/
  "esri/layers/VectorTileLayer",
  "dojo/domReady!"
], function(Map, MapView, VectorTileLayer) {

3. Now we'll add a vector tiled layer. To do that, we modify the code that creates the Map to just create an empty map and we'll add the tiled layer later.

  ...

  /*** REPLACE ***/

  // Create an empty map with no basemap
  var map = new Map();

  ...

  /*** ADD ***/

  // Create a new Vector Layer pointing at the style JSON.
  var tileLyr = new VectorTileLayer({
    url: "https://www.arcgis.com/sharing/rest/content/items/51acb8875f86482e82cb2ae24155b362/resources/styles/root.json"
  });

  map.add(tileLyr);

4. Confirm that the JSBin Output panel shows the vector tiles.

Your app should look something like this:

• Code
• Live App

###Bonus

• The 4.0 JS API works closely with ArcGIS Portals. Instead of the style JSON, you can create a Layer directly from the Portal Item. Use the same GUID as embededd in the code added in Step 3 above. You'll have to change the require module too.

  require([
    "esri/Map",
    "esri/views/MapView",
    // Reference the Layer module
    "esri/layers/Layer",
    "dojo/domReady!"
    // Provide a handle to "Layer"
  ], function(Map, MapView, Layer) {

  and

    Layer.fromPortalItem({
      portalItem: {
        id: "51acb8875f86482e82cb2ae24155b362"   
      }
    }).then(function(lyr){
      map.add(lyr);
    });

  Promise Pattern: You just used a Promise to do something asynchronously. The JS API asked ArcGIS Online for details about the item with ID 51acb8875f86482e82cb2ae24155b362. That took a round trip request to the ArcGIS.com servers. When the response came back, the JS API created the right type of layer as lyr and we added it to the map. Neat!

• The map in this lab doesn't have a basemap layer. Rather the VectorTileLayer is added as an operational layer. And that's OK, but might not be what you want.

  The 4.0 JS API has a powerful model of what a basemap is. Try using the custom VectorTileLayer as the basemap instead of calling map.add(). Look at the constructor for Map and the documentation for Basemap to see how to pass in a custom Basemap.

  With auto-casting, the JS API can make this quite convenient with something like this (where we auto-cast a Basemap object):

    var map = new Map({
      basemap: { // Auto-casting a Basemap
        baseLayers: [new VectorTileLayer({
          url: "https://www.arcgis.com/sharing/rest/content/items/51acb8875f86482e82cb2ae24155b362/resources/styles/root.json"
        })]  
      }
    });

  Or even (where we auto-cast a PortalItem and then a Basemap object):

    var map = new Map({
      basemap: { // Auto-casting a Basemap
        baseLayers: [new VectorTileLayer({
          portalItem: { // Auto-casting a PortalItem
            id: "51acb8875f86482e82cb2ae24155b362"   
          }
        })]  
      }
    });

  Auto-Casting: You just saw a couple examples of auto-casting at work (Basemap and PortalItem). As you look at samples, you'll probably see more. Simple JSON objects get turned into rich API objects. It makes working with the JS API quick and easy (you'll notice we didn't need to require the Basemap or PortalItem module for this to work.