Data Layer: Drag and Drop GeoJSON

This example allows you to drag and drop GeoJSON onto the map. Download a sample GeoJSON file to test dragging from the device.

For more information about how to work with the map data layer, see the google.maps.Data class.

TypeScript

let map: google.maps.Map;

function initMap(): void {
  // set up the map
  map = new google.maps.Map(document.getElementById("map") as HTMLElement, {
    center: new google.maps.LatLng(0, 0),
    zoom: 4,
  });
}

function loadGeoJsonString(geoString: string) {
  try {
    const geojson = JSON.parse(geoString) as any;

    map.data.addGeoJson(geojson);
  } catch (e) {
    alert("Not a GeoJSON file!");
  }

  zoom(map);
}

/**
 * Update a map's viewport to fit each geometry in a dataset
 */
function zoom(map: google.maps.Map) {
  const bounds = new google.maps.LatLngBounds();

  map.data.forEach((feature) => {
    const geometry = feature.getGeometry();

    if (geometry) {
      processPoints(geometry, bounds.extend, bounds);
    }
  });
  map.fitBounds(bounds);
}

/**
 * Process each point in a Geometry, regardless of how deep the points may lie.
 */
function processPoints(
  geometry: google.maps.LatLng | google.maps.Data.Geometry,
  callback: any,
  thisArg: google.maps.LatLngBounds
) {
  if (geometry instanceof google.maps.LatLng) {
    callback.call(thisArg, geometry);
  } else if (geometry instanceof google.maps.Data.Point) {
    callback.call(thisArg, geometry.get());
  } else {
    // @ts-ignore
    geometry.getArray().forEach((g) => {
      processPoints(g, callback, thisArg);
    });
  }
}

/* DOM (drag/drop) functions */
function initEvents() {
  [...document.getElementsByClassName("file")].forEach((fileElement) => {
    fileElement.addEventListener(
      "dragstart",
      (e: Event) => {
        // @ts-ignore
        e.dataTransfer.setData(
          "text/plain",
          JSON.stringify(files[Number((e.target as HTMLElement).dataset.value)])
        );
        console.log(e);
      },
      false
    );
  });

  // set up the drag & drop events
  const mapContainer = document.getElementById("map") as HTMLElement;

  mapContainer.addEventListener("dragenter", addClassToDropTarget, false);
  mapContainer.addEventListener("dragover", addClassToDropTarget, false);
  mapContainer.addEventListener("drop", handleDrop, false);
  mapContainer.addEventListener("dragleave", removeClassFromDropTarget, false);
}

function addClassToDropTarget(e: Event) {
  e.stopPropagation();
  e.preventDefault();
  document.getElementById("map")!.classList.add("over");
  return false;
}

function removeClassFromDropTarget(e: Event) {
  document.getElementById("map")!.classList.remove("over");
}

function handleDrop(e: DragEvent) {
  e.preventDefault();
  e.stopPropagation();
  removeClassFromDropTarget(e);

  const files = (e.dataTransfer as DataTransfer).files;

  if (files.length) {
    // process file(s) being dropped
    // grab the file data from each file
    for (let i = 0, file; (file = files[i]); i++) {
      const reader = new FileReader();

      reader.onload = function (e) {
        loadGeoJsonString(reader.result as string);
      };

      reader.onerror = function (e) {
        console.error("reading failed");
      };

      reader.readAsText(file);
    }
  } else {
    // process non-file (e.g. text or html) content being dropped
    // grab the plain text version of the data
    const plainText = (e.dataTransfer as DataTransfer).getData("text/plain");

    console.log(plainText);

    if (plainText) {
      loadGeoJsonString(plainText);
    }
  }

  // prevent drag event from bubbling further
  return false;
}

function initialize() {
  initMap();
  initEvents();
}

const files = [
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Polygon",
          coordinates: [
            [
              [-99.49218749999999, -11.867350911459294],
              [24.960937499999996, -11.867350911459294],
              [24.960937499999996, 47.517200697839414],
              [-99.49218749999999, 47.517200697839414],
              [-99.49218749999999, -11.867350911459294],
            ],
          ],
        },
      },
    ],
  },
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [81.2109375, 50.064191736659104],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [103.35937499999999, -47.98992166741417],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-46.05468749999999, 64.01449619484472],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-113.203125, 37.996162679728116],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-73.828125, -32.249974455863295],
        },
      },
    ],
  },
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "LineString",
          coordinates: [
            [147.65625, -5.266007882805485],
            [118.47656249999999, 43.83452678223682],
            [80.85937499999999, -30.145127183376115],
            [35.15625, 51.83577752045248],
            [-15.468749999999998, -23.563987128451217],
            [-29.53125, 44.33956524809713],
            [-73.47656249999999, -32.842673631954305],
            [-104.765625, 35.460669951495305],
          ],
        },
      },
    ],
  },
];

declare global {
  interface Window {
    initialize: () => void;
  }
}
window.initialize = initialize;
index.ts

Note: Read the guide on using TypeScript and Google Maps.

JavaScript

let map;

function initMap() {
  // set up the map
  map = new google.maps.Map(document.getElementById("map"), {
    center: new google.maps.LatLng(0, 0),
    zoom: 4,
  });
}

function loadGeoJsonString(geoString) {
  try {
    const geojson = JSON.parse(geoString);

    map.data.addGeoJson(geojson);
  } catch (e) {
    alert("Not a GeoJSON file!");
  }

  zoom(map);
}

/**
 * Update a map's viewport to fit each geometry in a dataset
 */
function zoom(map) {
  const bounds = new google.maps.LatLngBounds();

  map.data.forEach((feature) => {
    const geometry = feature.getGeometry();

    if (geometry) {
      processPoints(geometry, bounds.extend, bounds);
    }
  });
  map.fitBounds(bounds);
}

/**
 * Process each point in a Geometry, regardless of how deep the points may lie.
 */
function processPoints(geometry, callback, thisArg) {
  if (geometry instanceof google.maps.LatLng) {
    callback.call(thisArg, geometry);
  } else if (geometry instanceof google.maps.Data.Point) {
    callback.call(thisArg, geometry.get());
  } else {
    // @ts-ignore
    geometry.getArray().forEach((g) => {
      processPoints(g, callback, thisArg);
    });
  }
}

/* DOM (drag/drop) functions */
function initEvents() {
  [...document.getElementsByClassName("file")].forEach((fileElement) => {
    fileElement.addEventListener(
      "dragstart",
      (e) => {
        // @ts-ignore
        e.dataTransfer.setData(
          "text/plain",
          JSON.stringify(files[Number(e.target.dataset.value)]),
        );
        console.log(e);
      },
      false,
    );
  });

  // set up the drag & drop events
  const mapContainer = document.getElementById("map");

  mapContainer.addEventListener("dragenter", addClassToDropTarget, false);
  mapContainer.addEventListener("dragover", addClassToDropTarget, false);
  mapContainer.addEventListener("drop", handleDrop, false);
  mapContainer.addEventListener("dragleave", removeClassFromDropTarget, false);
}

function addClassToDropTarget(e) {
  e.stopPropagation();
  e.preventDefault();
  document.getElementById("map").classList.add("over");
  return false;
}

function removeClassFromDropTarget(e) {
  document.getElementById("map").classList.remove("over");
}

function handleDrop(e) {
  e.preventDefault();
  e.stopPropagation();
  removeClassFromDropTarget(e);

  const files = e.dataTransfer.files;

  if (files.length) {
    // process file(s) being dropped
    // grab the file data from each file
    for (let i = 0, file; (file = files[i]); i++) {
      const reader = new FileReader();

      reader.onload = function (e) {
        loadGeoJsonString(reader.result);
      };

      reader.onerror = function (e) {
        console.error("reading failed");
      };

      reader.readAsText(file);
    }
  } else {
    // process non-file (e.g. text or html) content being dropped
    // grab the plain text version of the data
    const plainText = e.dataTransfer.getData("text/plain");

    console.log(plainText);
    if (plainText) {
      loadGeoJsonString(plainText);
    }
  }
  // prevent drag event from bubbling further
  return false;
}

function initialize() {
  initMap();
  initEvents();
}

const files = [
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Polygon",
          coordinates: [
            [
              [-99.49218749999999, -11.867350911459294],
              [24.960937499999996, -11.867350911459294],
              [24.960937499999996, 47.517200697839414],
              [-99.49218749999999, 47.517200697839414],
              [-99.49218749999999, -11.867350911459294],
            ],
          ],
        },
      },
    ],
  },
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [81.2109375, 50.064191736659104],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [103.35937499999999, -47.98992166741417],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-46.05468749999999, 64.01449619484472],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-113.203125, 37.996162679728116],
        },
      },
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "Point",
          coordinates: [-73.828125, -32.249974455863295],
        },
      },
    ],
  },
  {
    type: "FeatureCollection",
    features: [
      {
        type: "Feature",
        properties: {},
        geometry: {
          type: "LineString",
          coordinates: [
            [147.65625, -5.266007882805485],
            [118.47656249999999, 43.83452678223682],
            [80.85937499999999, -30.145127183376115],
            [35.15625, 51.83577752045248],
            [-15.468749999999998, -23.563987128451217],
            [-29.53125, 44.33956524809713],
            [-73.47656249999999, -32.842673631954305],
            [-104.765625, 35.460669951495305],
          ],
        },
      },
    ],
  },
];

window.initialize = initialize;
index.js

Note: The JavaScript is compiled from the TypeScript snippet.

CSS

html {
  height: 100%;
}

body {
  height: 100%;
  margin: 0;
  padding: 0;
  overflow: hidden;
}

#map {
  height: 100%;
}
#map.over {
  opacity: 0.5;
  background-color: rgba(100, 100, 100, 0.5);
}

#sidebar {
  flex-direction: column;
  align-items: center;
  justify-content: center;
  overflow: auto;
}

.file {
  display: flex;
  flex-flow: column;
  margin-top: 1em;
  cursor: move;
  text-align: center;
}
.file:hover .material-icons {
  color: darkorange;
}
.file:hover .filename {
  font-weight: bold;
}
.file .material-icons {
  font-size: 50px;
  color: orange;
}
.file .material-icons:hover {
  color: darkorange;
}
.file .filename {
  margin-top: 0.5em;
  font-size: 20px;
  color: #333333;
}

/* Optional: Makes the sample page fill the window. */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

#container {
  height: 100%;
  display: flex;
}

#sidebar {
  flex-basis: 15rem;
  flex-grow: 1;
  padding: 1rem;
  max-width: 30rem;
  height: 100%;
  box-sizing: border-box;
  overflow: auto;
}

#map {
  flex-basis: 0;
  flex-grow: 4;
  height: 100%;
}
style.css

HTML

<html>
  <head>
    <title>Data Layer: Drag and Drop GeoJSON</title>

    <link
      href="https://unpkg.com/material-components-web@6.0.0/dist/material-components-web.css"
      rel="stylesheet"
    />
    <link
      rel="stylesheet"
      href="https://fonts.googleapis.com/icon?family=Material+Icons"
    />

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <div id="container">
      <div id="map"></div>
      <div id="sidebar" class="mdc-typography">
        <div class="file" draggable="true" data-value="0">
          <span class="material-icons">text_snippet</span>
          <div class="filename">polygons.geojson</div>
        </div>
        <div class="file" draggable="true" data-value="1">
          <span class="material-icons">text_snippet</span>
          <div class="filename">points.geojson</div>
        </div>
        <div class="file" draggable="true" data-value="2">
          <span class="material-icons">text_snippet</span>
          <div class="filename">polyline.geojson</div>
        </div>
      </div>
    </div>

    <!-- 
      The `defer` attribute causes the script to execute after the full HTML
      document has been parsed. For non-blocking uses, avoiding race conditions,
      and consistent behavior across browsers, consider loading using Promises. See
      https://developers.google.com/maps/documentation/javascript/load-maps-js-api
      for more information.
      -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initialize&v=weekly"
      defer
    ></script>
  </body>
</html>
index.html

Try Sample

JSFiddle.net Google Cloud Shell

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application.

  git clone -b sample-layer-data-dragndrop https://github.com/googlemaps/js-samples.git
  cd js-samples
  npm i
  npm start

Other samples can be tried by switching to any branch beginning with sample-SAMPLE_NAME.

  git checkout sample-SAMPLE_NAME
  npm i
  npm start