require([

  "esri/Map",

  "esri/views/MapView",

  "esri/layers/FeatureLayer",

  "esri/layers/GroupLayer",

  "dojo/domReady!"

], function (Map, MapView, FeatureLayer, GroupLayer) {

​

  var url = "http://tmservices1.esri.com/arcgis/rest/services/LiveFeeds/NOAA_storm_reports/MapServer/";

​

  var map = new Map({

    basemap: "streets"

  });

​

  var view = new MapView({

    container: "viewDiv",

    map: map,

    center: [-98.648, 36.374],

    zoom: 5,

    ui: {

      components: ["zoom", "attribution", "compass"]

    }

  });

​

  var titles = [

    "NOAA HAIL Storm Reports (24 hours)",

    "NOAA TORNADO Storm Reports (24 hours)",

    "NOAA WIND Storm Reports (24 hours)",

    "NOAA TORNADO Storm Reports (past week)"

  ];

​

  var layers = ["0", "1", "2", "3"].map(function(index, idx) {

    return new FeatureLayer({

      url: url + index,

      outFields: ["*"],

      popupTemplate: {

        title: titles[idx],

        content: "{*}"

      }

    });

  });

​

  var groupLayer = new GroupLayer({

    layers: layers,

    visibilityMode: "inherited",

    visible: true

  });

  map.add(groupLayer);

​

  view.then(function() {

    var btn = document.createElement("div");

    btn.className = "esri-button esri-widget-button esri-interactive esri-icon-feature-layer";

    btn.title = "Toggle Storm Data";

    view.ui.add(btn, "top-right");

    btn.addEventListener("click", function() {

      groupLayer.visible = !groupLayer.visible;

    });

  });

});