develop/jsapi/style_feature_layer/index.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
  <title>Style Feature Layer</title>

  <link rel="stylesheet" href="https://js.arcgis.com/4.1/esri/css/main.css">

  <style>
    html, body, #viewDiv {
      padding: 0;
      margin: 0;
      height: 100%;
    }
  </style>

  <script src="https://js.arcgis.com/4.1/"></script>

  <script>
    require([
      "esri/Map",
      "esri/views/MapView",
      "esri/layers/FeatureLayer",
      "esri/symbols/SimpleLineSymbol",
      "esri/renderers/UniqueValueRenderer",
      "dojo/domReady!"
    ], function(Map, MapView, FeatureLayer, SimpleLineSymbol, UniqueValueRenderer) {

      var map = new Map({
        basemap: "dark-gray"
      });

      var view = new MapView({
        container: "viewDiv",
        map: map,
        center: [-122.68, 45.52],
        zoom: 10
      });

      var renderer = new UniqueValueRenderer({
        field: "TYPE",
        defaultSymbol: new SimpleLineSymbol()
      });

      renderer.addUniqueValueInfo("MAX",
        new SimpleLineSymbol({
          color: [96, 219, 34, 0.8]
        })
      );

      renderer.addUniqueValueInfo("SC",
        new SimpleLineSymbol({
          color: [255, 255, 34, 0.8]
        })
      );

      renderer.addUniqueValueInfo("MAX/SC",
        new SimpleLineSymbol({
          color: [238, 71, 71, 0.8]
        })
      );

      renderer.addUniqueValueInfo("CR",
        new SimpleLineSymbol({
          color: [8, 197, 249, 1],
          width: 4
        })
      );

      var featureLayer = new FeatureLayer({
        url: "https://services.arcgis.com/uCXeTVveQzP4IIcx/arcgis/rest/services/PDX_Rail_Lines/FeatureServer/0",
        renderer: renderer 
      });

      map.add(featureLayer);
    });
  </script>
</head>
<body>
  <div id="viewDiv"></div>
</body>
</html>