Merge pull request #748 from jennyphan/master

Update MarkerClusterer.md to not use index as key

Author: JustFly1984

packages/react-google-maps-api/src/components/addons/MarkerClusterer.md

@@ -1,63 +1,57 @@
 # MarkerClusterer example
 
 ```jsx
-const { GoogleMap, LoadScript, MarkerClusterer, Marker } = require("../../");
-const ScriptLoaded = require("../../docs/ScriptLoaded").default;
+const { GoogleMap, LoadScript, MarkerClusterer, Marker } = require('../../')
+const ScriptLoaded = require('../../docs/ScriptLoaded').default
 
 const mapContainerStyle = {
-  height: "400px",
-  width: "800px"
-};
+  height: '400px',
+  width: '800px',
+}
 
-const center = { lat: -28.024, lng: 140.887 };
+const center = { lat: -28.024, lng: 140.887 }
 
 const locations = [
-  {lat: -31.563910, lng: 147.154312},
-  {lat: -33.718234, lng: 150.363181},
-  {lat: -33.727111, lng: 150.371124},
-  {lat: -33.848588, lng: 151.209834},
-  {lat: -33.851702, lng: 151.216968},
-  {lat: -34.671264, lng: 150.863657},
-  {lat: -35.304724, lng: 148.662905},
-  {lat: -36.817685, lng: 175.699196},
-  {lat: -36.828611, lng: 175.790222},
-  {lat: -37.750000, lng: 145.116667},
-  {lat: -37.759859, lng: 145.128708},
-  {lat: -37.765015, lng: 145.133858},
-  {lat: -37.770104, lng: 145.143299},
-  {lat: -37.773700, lng: 145.145187},
-  {lat: -37.774785, lng: 145.137978},
-  {lat: -37.819616, lng: 144.968119},
-  {lat: -38.330766, lng: 144.695692},
-  {lat: -39.927193, lng: 175.053218},
-  {lat: -41.330162, lng: 174.865694},
-  {lat: -42.734358, lng: 147.439506},
-  {lat: -42.734358, lng: 147.501315},
-  {lat: -42.735258, lng: 147.438000},
-  {lat: -43.999792, lng: 170.463352}
-];
+  { lat: -31.56391, lng: 147.154312 },
+  { lat: -33.718234, lng: 150.363181 },
+  { lat: -33.727111, lng: 150.371124 },
+  { lat: -33.848588, lng: 151.209834 },
+  { lat: -33.851702, lng: 151.216968 },
+  { lat: -34.671264, lng: 150.863657 },
+  { lat: -35.304724, lng: 148.662905 },
+  { lat: -36.817685, lng: 175.699196 },
+  { lat: -36.828611, lng: 175.790222 },
+  { lat: -37.75, lng: 145.116667 },
+  { lat: -37.759859, lng: 145.128708 },
+  { lat: -37.765015, lng: 145.133858 },
+  { lat: -37.770104, lng: 145.143299 },
+  { lat: -37.7737, lng: 145.145187 },
+  { lat: -37.774785, lng: 145.137978 },
+  { lat: -37.819616, lng: 144.968119 },
+  { lat: -38.330766, lng: 144.695692 },
+  { lat: -39.927193, lng: 175.053218 },
+  { lat: -41.330162, lng: 174.865694 },
+  { lat: -42.734358, lng: 147.439506 },
+  { lat: -42.734358, lng: 147.501315 },
+  { lat: -42.735258, lng: 147.438 },
+  { lat: -43.999792, lng: 170.463352 },
+]
 
-const options = { 
-  imagePath:"https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m" 
-};
+const options = {
+  imagePath:
+    'https://developers.google.com/maps/documentation/javascript/examples/markerclusterer/m',
+}
 
-<ScriptLoaded>
-  <GoogleMap
-    id="marker-example"
-    mapContainerStyle={mapContainerStyle}
-    zoom={3}
-    center={center}
-  >
-    <MarkerClusterer
-      options={options}
-    >
-      {
-        (clusterer) => locations.map((location, i) => (
-          <Marker
-            key={i}
-            position={location}
-            clusterer={clusterer}
-          />
+function createKey(location: { lat: number, lng: number }): React.ReactText {
+  return location.lat + location.lng
+}
+
+;<ScriptLoaded>
+  <GoogleMap id='marker-example' mapContainerStyle={mapContainerStyle} zoom={3} center={center}>
+    <MarkerClusterer options={options}>
+      {clusterer =>
+        locations.map(location => (
+          <Marker key={createKey(location)} position={location} clusterer={clusterer} />
         ))
       }
     </MarkerClusterer>