Query client and server-side (Turf.js)

Esri Leaflet works with client-side libraries that can perform spatial analysis in the browser like Turf.js. This demo shows how the output from a spatial query can be augmented to isolate features that have a spatial relationship with another arbitrary geometry.
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<html>
  <head>
    <meta charset="utf-8" />
    <title>Query client and server-side (Turf.js)</title>
    <meta name="viewport" content="initial-scale=1, maximum-scale=1, user-scalable=no" />
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" crossorigin="" />
    <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js" crossorigin=""></script>
    <!-- Load Esri Leaflet from CDN -->
    <script src="https://unpkg.com/esri-leaflet@3.0.12/dist/esri-leaflet.js"></script>
    <!-- Load Esri Leaflet Vector from CDN -->
    <script src="https://unpkg.com/esri-leaflet-vector@4.2.5/dist/esri-leaflet-vector.js" crossorigin=""></script>
    <style>
      html,
      body,
      #map {
        padding: 0;
        margin: 0;
        height: 100%;
        width: 100%;
        font-family: Arial, Helvetica, sans-serif;
        font-size: 14px;
        color: #323232;
      }
    </style>
  </head>
  <body>
    <script src="https://unpkg.com/@turf/turf@5.1.6/turf.min.js"></script>
    <style>
      #info-pane {
        position: absolute;
        top: 10px;
        right: 10px;
        z-index: 1000;
        padding: 1em;
        background: white;
        max-width: 150px;
      }
    </style>
    <div id="map"></div>
    <div id="info-pane" class="leaflet-bar">
      <label> Census block points that intersect both bounding boxes are red. </label>
    </div>
    <script type="text/javascript">
      const accessToken = "YOUR_ACCESS_TOKEN";

     const boundingBoxes = { //Two GeoJSON bounding boxes
        type: "FeatureCollection",
        features: [
          {
            type: "Feature",
            properties: {
              color: "orange"
            },
            geometry: {
              type: "Polygon",
              coordinates: [
                [
                  [-84.39010620117188, 33.747965492070236],
                  [-84.39010620117188, 33.75431694675655],
                  [-84.37311172485352, 33.75431694675655],
                  [-84.37311172485352, 33.747965492070236],
                  [-84.39010620117188, 33.747965492070236]
                ]
              ]
            }
          },
          {
            type: "Feature",
            properties: {
              color: "#0ceb70"
            },
            geometry: {
              type: "Polygon",
              coordinates: [
                [
                  [-84.39963340759277, 33.744254312044156],
                  [-84.39963340759277, 33.75817040902938],
                  [-84.38444137573242, 33.75817040902938],
                  [-84.38444137573242, 33.744254312044156],
                  [-84.39963340759277, 33.744254312044156]
                ]
              ]
            }
          }
        ]
      };

     const map = L.map("map").setView([33.752, -84.385], 14.5);

      L.esri.Vector.vectorBasemapLayer("arcgis/imagery/standard", {
        token: accessToken
      }).addTo(map);

      L.geoJSON(boundingBoxes, { //Display the bounding boxes on the map
        style: function (feature) {
          return { color: feature.properties.color };
        }
      }).addTo(map);

      const query = L.esri.query({
        url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/0"
      });
      query.intersects(boundingBoxes.features[0]);

      query.run(function (err, censusCollection, raw) {
        if (err) {
          return;
        }
        const features = censusCollection.features;

        for (let i = 0; i < features.length; i++) {
          if (turf.inside(features[i], boundingBoxes.features[1])) {
            L.geoJSON(features[i], {
              pointToLayer: function (geoJsonPoint, latlng) {
                return L.circleMarker(latlng, {
                  color: "#ff0066"
                });
              }
            }).addTo(map);
          } else {
            L.geoJSON(features[i], { //If the smaller box is not contained by the bigger box, make it gray and partially transparent.
              pointToLayer: function (geoJsonPoint, latlng) {
                return L.circleMarker(latlng, {
                  radius: 10,
                  color: "gray",
                  opacity: 0.2
                });
              }
            }).addTo(map);
          }
        }
      });
    </script>
  </body>
</html>