Capture attribute values from a WebMap without click event

LA

Hi,
I have a general question about how to capture attribute values from a WebMap (using API 4.x) without using click events on the map (this thread #Capture attribute values from a WebMap has an excellent solution using the click event and the hitTest method, but now I need to access attribute values without having to click on the map).

This thread #Access ArcGIS Server database content from JavaScript application has a solution based on QueryTask (API 3.22), but I don't know what this object maps to in API 4.4.

I am also not aware of having access to a REST service associated with this WebMap, and I am not familiar with the ArcGIS framework, but if I have access to a WebMap through the portalItem property, does that mean that I should get access to a REST service too? Is there a way I can access the attribute values without setting up a REST service?

I would also like to avoid using the FeatureLayer object since my web application resides in a different domain than the ArcGIS server and when I try to use FeatureLayer I get a CORS error.

I apologize for the vagueness but thanks for your help,

LA

I am also a bit confused why 

console<SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">.</SPAN><SPAN class="" style="color: #d74444; border: 0px; font-weight: inherit;">log</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">(</SPAN><SPAN class="" style="color: #669900; border: 0px; font-weight: inherit;">"Num WebMap Layers: "</SPAN><SPAN class="" style="color: #a67f59; background: rgba(255, 255, 255, 0.5); border: 0px; font-weight: inherit;">+</SPAN>webmap<SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">.</SPAN>layers<SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">.</SPAN>length<SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">)</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit;">;</SPAN>

displays zero for number of WebMap layers, I guess they are embedded differently into the WebMap?

My current code:

<SPAN class="token function">require</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>
 <SPAN class="string token">"esri/views/MapView"</SPAN><SPAN class="punctuation token">,</SPAN>
 <SPAN class="string token">"esri/WebMap"</SPAN><SPAN class="punctuation token">,</SPAN>
 <SPAN class="string token">"dojo/domReady!"</SPAN>
 <SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>MapView<SPAN class="punctuation token">,</SPAN> WebMap<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
<SPAN class="comment token">/************************************************************
 * Creates a new WebMap instance. A WebMap must reference
 * a PortalItem ID that represents a WebMap saved to
 * arcgis.com or an on-premise portal.
 ************************************************************/</SPAN>
 <SPAN class="keyword token">var</SPAN> webmap <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">WebMap</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">{</SPAN>
 portalItem<SPAN class="punctuation token">:</SPAN> <SPAN class="punctuation token">{</SPAN> <SPAN class="comment token">// autocasts as new PortalItem()</SPAN>
 id<SPAN class="punctuation token">:</SPAN> <SPAN class="string token">"7faf8d05df114f8082411414382c69d3"</SPAN>
 <SPAN class="comment token">//id: "65de4dd5bbfb4c0dbac85d395052bee3" // Speed Studies Web Map</SPAN>
 <SPAN class="punctuation token">}</SPAN>
 <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="comment token">/************************************************************
 * Set the WebMap instance to the map property in a MapView.
 ************************************************************/</SPAN>
 <SPAN class="keyword token">var</SPAN> view <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">MapView</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">{</SPAN>
 map<SPAN class="punctuation token">:</SPAN> webmap<SPAN class="punctuation token">,</SPAN>
 container<SPAN class="punctuation token">:</SPAN> <SPAN class="string token">"viewMap"</SPAN>
 <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
view<SPAN class="punctuation token">.</SPAN><SPAN class="token function">on</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"click"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>event<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN> 
 view<SPAN class="punctuation token">.</SPAN><SPAN class="token function">hitTest</SPAN><SPAN class="punctuation token">(</SPAN>event<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">then</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>evt<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
 <SPAN class="keyword token">if</SPAN><SPAN class="punctuation token">(</SPAN>evt<SPAN class="punctuation token">.</SPAN>results<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
 console<SPAN class="punctuation token">.</SPAN><SPAN class="token function">log</SPAN><SPAN class="punctuation token">(</SPAN>evt<SPAN class="punctuation token">.</SPAN>results<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>graphic<SPAN class="punctuation token">.</SPAN>attributes<SPAN class="punctuation token">[</SPAN><SPAN class="string token">"Type"</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 console<SPAN class="punctuation token">.</SPAN><SPAN class="token function">log</SPAN><SPAN class="punctuation token">(</SPAN>evt<SPAN class="punctuation token">.</SPAN>results<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>graphic<SPAN class="punctuation token">.</SPAN>geometry<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="keyword token">if</SPAN><SPAN class="punctuation token">(</SPAN>evt<SPAN class="punctuation token">.</SPAN>results<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>graphic<SPAN class="punctuation token">.</SPAN>attributes<SPAN class="punctuation token">[</SPAN><SPAN class="string token">"Type"</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="operator token">!=</SPAN><SPAN class="string token">"B"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
 <SPAN class="token function">$</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"#startPt"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">css</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"background-color"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"red"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="punctuation token">}</SPAN>
 <SPAN class="keyword token">else</SPAN><SPAN class="punctuation token">{</SPAN>
 <SPAN class="token function">$</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"#startPt"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">css</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"background-color"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"transparent"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="punctuation token">}</SPAN>
 <SPAN class="punctuation token">}</SPAN>
 <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
 <SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>script<SPAN class="operator token">></SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

rscheitlin

L A,

  So You have a lot of questions here and the easiest way to answer them all is with a sample that shows how.

<SPAN class="operator token"><</SPAN><SPAN class="operator token">!</SPAN>DOCTYPE html<SPAN class="operator token">></SPAN>
<SPAN class="operator token"><</SPAN>html<SPAN class="operator token">></SPAN>
<SPAN class="operator token"><</SPAN>head<SPAN class="operator token">></SPAN>
&nbsp; <SPAN class="operator token"><</SPAN>meta charset<SPAN class="operator token">=</SPAN><SPAN class="string token">"utf-8"</SPAN><SPAN class="operator token">></SPAN>
&nbsp; <SPAN class="operator token"><</SPAN>meta name<SPAN class="operator token">=</SPAN><SPAN class="string token">"viewport"</SPAN> content<SPAN class="operator token">=</SPAN><SPAN class="string token">"initial-scale=1,maximum-scale=1,user-scalable=no"</SPAN><SPAN class="operator token">></SPAN>
&nbsp; <SPAN class="operator token"><</SPAN>title<SPAN class="operator token">></SPAN>Load a basic WebMap <SPAN class="operator token">-</SPAN> <SPAN class="number token">4.5</SPAN><SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>title<SPAN class="operator token">></SPAN>

&nbsp; <SPAN class="operator token"><</SPAN>style<SPAN class="operator token">></SPAN>
&nbsp;&nbsp;&nbsp; html<SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp; body<SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp; #viewDiv <SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; padding<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; margin<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; height<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">100</SPAN><SPAN class="operator token">%</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; width<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">100</SPAN><SPAN class="operator token">%</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN>
&nbsp; <SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>style<SPAN class="operator token">></SPAN>

&nbsp; <SPAN class="operator token"><</SPAN>link rel<SPAN class="operator token">=</SPAN><SPAN class="string token">"stylesheet"</SPAN> href<SPAN class="operator token">=</SPAN><SPAN class="string token"><SPAN>"</SPAN><A class="jive-link-external-small" href="https://community.esri.com/external-link.jspa?url=https%3A%2F%2Fjs.arcgis.com%2F4.5%2Fesri%2Fcss%2Fmain.css" target="_blank">https://js.arcgis.com/4.5/esri/css/main.css</A><SPAN>"</SPAN></SPAN><SPAN class="operator token">></SPAN>

&nbsp; <SPAN class="operator token"><</SPAN>script src<SPAN class="operator token">=</SPAN><SPAN class="string token"><SPAN>"</SPAN><A class="jive-link-external-small" href="https://community.esri.com/external-link.jspa?url=https%3A%2F%2Fjs.arcgis.com%2F4.5%2F" target="_blank">https://js.arcgis.com/4.5/</A><SPAN>"</SPAN></SPAN><SPAN class="operator token">></SPAN><SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>script<SPAN class="operator token">></SPAN>

&nbsp; <SPAN class="operator token"><</SPAN>script<SPAN class="operator token">></SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="token function">require</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="string token">"esri/views/MapView"</SPAN><SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="string token">"esri/WebMap"</SPAN><SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="string token">"esri/tasks/support/Query"</SPAN><SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="string token">"dojo/domReady!"</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; MapView<SPAN class="punctuation token">,</SPAN> WebMap<SPAN class="punctuation token">,</SPAN> Query
&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">/************************************************************
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * Creates a new WebMap instance. A WebMap must reference
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * a PortalItem ID that represents a WebMap saved to
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * arcgis.com or an on-premise portal.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * To load a WebMap from an on-premise portal, set the portal
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * url with esriConfig.portalUrl.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ************************************************************/</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">var</SPAN> webmap <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">WebMap</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; portalItem<SPAN class="punctuation token">:</SPAN> <SPAN class="punctuation token">{</SPAN> <SPAN class="comment token">// autocasts as new PortalItem()</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; id<SPAN class="punctuation token">:</SPAN> <SPAN class="string token">"f2e9b762544945f390ca4ac3671cfa72"</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token">/************************************************************
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; * Set the WebMap instance to the map property in a MapView.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ************************************************************/</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">var</SPAN> view <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">MapView</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; map<SPAN class="punctuation token">:</SPAN> webmap<SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; container<SPAN class="punctuation token">:</SPAN> <SPAN class="string token">"viewDiv"</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; webmap<SPAN class="punctuation token">.</SPAN><SPAN class="token function">then</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">var</SPAN> query <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">new</SPAN> <SPAN class="token class-name">Query</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; query<SPAN class="punctuation token">.</SPAN>where <SPAN class="operator token">=</SPAN> <SPAN class="string token">'1=1'</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; query<SPAN class="punctuation token">.</SPAN>outSpatialReference <SPAN class="operator token">=</SPAN> view<SPAN class="punctuation token">.</SPAN>spatialReference<SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; query<SPAN class="punctuation token">.</SPAN>outFields <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"*"</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; webmap<SPAN class="punctuation token">.</SPAN>layers<SPAN class="punctuation token">.</SPAN><SPAN class="token function">map</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>lyr<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; lyr<SPAN class="punctuation token">.</SPAN><SPAN class="token function">queryFeatures</SPAN><SPAN class="punctuation token">(</SPAN>query<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="token function">then</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">function</SPAN><SPAN class="punctuation token">(</SPAN>results<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">{</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; console<SPAN class="punctuation token">.</SPAN><SPAN class="token function">info</SPAN><SPAN class="punctuation token">(</SPAN>results<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">}</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
&nbsp; <SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>script<SPAN class="operator token">></SPAN>
<SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>head<SPAN class="operator token">></SPAN>

<SPAN class="operator token"><</SPAN>body<SPAN class="operator token">></SPAN>
&nbsp; <SPAN class="operator token"><</SPAN>div id<SPAN class="operator token">=</SPAN><SPAN class="string token">"viewDiv"</SPAN><SPAN class="operator token">></SPAN><SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>div<SPAN class="operator token">></SPAN>
<SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>body<SPAN class="operator token">></SPAN>

<SPAN class="operator token"><</SPAN><SPAN class="operator token">/</SPAN>html<SPAN class="operator token">></SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

The reason that webmap.layers.length was 0 is that you were not waiting for the webmap to initialize (line 55 above).

The above sample waits for the webmap then loops though the layers and performs a query on each layer to return all the features in that layer and console log them. So this is how you work with layer in a web map. Also if you console log the layer you will see a property called url which is the url of the layer that you could use to Query the layer using the QueryTask, but as a FeatureLayer has a queryFeatures method it is just easier to do it as above.