 "esri/layers/VectorTileLayer",
             "dojo/domReady!"],
      function(Map, VectorTileLayer) {
        map = new Map("mapDiv", {
          center: [-122.68, 45.52],
          zoom: 10
          //basemap: "dark-gray" // Do not set a basemap
        });

      //The URL referenced in the constructor may point to a style JSON object in ArcGIS Online or directly to a vector tile service.
        var vtlayer = new VectorTileLayer("https://www.arcgis.com/sharing/rest/content/items/51acb8875f86482e82cb2ae