Resizable Split Map Panes

Comparing layers

This example allows comparison of two layers with resizable map panes using the Split.js library.

TypeScript

function initMap(): void {
  const mapOptions = {
    center: { lat: 44.5250489, lng: -110.83819 },
    zoom: 18,
    scaleControl: false,
    streetViewControl: false,
  };

  // instantiate the map on the left with control positioning
  mapLeft = new google.maps.Map(
    document.getElementById("map-left") as HTMLElement,
    {
      ...mapOptions,
      mapTypeId: "satellite",
      tilt: 0, // at high zoom levels we need to maintain the same projection
      fullscreenControlOptions: {
        position: google.maps.ControlPosition.LEFT_BOTTOM,
      },
      mapTypeControlOptions: {
        position: google.maps.ControlPosition.LEFT_TOP,
      },
      zoomControlOptions: {
        position: google.maps.ControlPosition.LEFT_BOTTOM,
      },
    }
  );

  // instantiate the map on the right with control positioning
  mapRight = new google.maps.Map(
    document.getElementById("map-right") as HTMLElement,
    {
      ...mapOptions,
      fullscreenControlOptions: {
        position: google.maps.ControlPosition.RIGHT_BOTTOM,
      },
      mapTypeControlOptions: {
        position: google.maps.ControlPosition.RIGHT_TOP,
      },
      zoomControlOptions: {
        position: google.maps.ControlPosition.RIGHT_BOTTOM,
      },
    }
  );

  // helper function to keep maps in sync
  function sync(...maps: google.maps.Map[]) {
    let center: google.maps.LatLng, zoom: number;

    function update(changedMap) {
      maps.forEach((m) => {
        if (m === changedMap) {
          return;
        }

        m.setCenter(center);
        m.setZoom(zoom);
      });
    }

    maps.forEach((m) => {
      m.addListener("bounds_changed", () => {
        const changedCenter = m.getCenter()!;
        const changedZoom = m.getZoom()!;

        if (changedCenter !== center || changedZoom !== zoom) {
          center = changedCenter;
          zoom = changedZoom;
          update(m);
        }
      });
    });
  }

  sync(mapLeft, mapRight);

  function handleContainerResize() {
    const width = (document.getElementById("container") as HTMLElement)
      .offsetWidth;

    (
      document.getElementById("map-left") as HTMLElement
    ).style.width = `${width}px`;
    (
      document.getElementById("map-right") as HTMLElement
    ).style.width = `${width}px`;
  }

  // trigger to set map container size since using absolute
  handleContainerResize();
  // add event listener
  window.addEventListener("resize", handleContainerResize);

  //@ts-ignore
  Split(["#left", "#right"], {
    sizes: [50, 50],
  });
}

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

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

JavaScript

function initMap() {
  const mapOptions = {
    center: { lat: 44.5250489, lng: -110.83819 },
    zoom: 18,
    scaleControl: false,
    streetViewControl: false,
  };

  // instantiate the map on the left with control positioning
  mapLeft = new google.maps.Map(document.getElementById("map-left"), {
    ...mapOptions,
    mapTypeId: "satellite",
    tilt: 0,
    fullscreenControlOptions: {
      position: google.maps.ControlPosition.LEFT_BOTTOM,
    },
    mapTypeControlOptions: {
      position: google.maps.ControlPosition.LEFT_TOP,
    },
    zoomControlOptions: {
      position: google.maps.ControlPosition.LEFT_BOTTOM,
    },
  });
  // instantiate the map on the right with control positioning
  mapRight = new google.maps.Map(document.getElementById("map-right"), {
    ...mapOptions,
    fullscreenControlOptions: {
      position: google.maps.ControlPosition.RIGHT_BOTTOM,
    },
    mapTypeControlOptions: {
      position: google.maps.ControlPosition.RIGHT_TOP,
    },
    zoomControlOptions: {
      position: google.maps.ControlPosition.RIGHT_BOTTOM,
    },
  });

  // helper function to keep maps in sync
  function sync(...maps) {
    let center, zoom;

    function update(changedMap) {
      maps.forEach((m) => {
        if (m === changedMap) {
          return;
        }

        m.setCenter(center);
        m.setZoom(zoom);
      });
    }

    maps.forEach((m) => {
      m.addListener("bounds_changed", () => {
        const changedCenter = m.getCenter();
        const changedZoom = m.getZoom();

        if (changedCenter !== center || changedZoom !== zoom) {
          center = changedCenter;
          zoom = changedZoom;
          update(m);
        }
      });
    });
  }

  sync(mapLeft, mapRight);

  function handleContainerResize() {
    const width = document.getElementById("container").offsetWidth;

    document.getElementById("map-left").style.width = `${width}px`;
    document.getElementById("map-right").style.width = `${width}px`;
  }

  // trigger to set map container size since using absolute
  handleContainerResize();
  // add event listener
  window.addEventListener("resize", handleContainerResize);
  //@ts-ignore
  Split(["#left", "#right"], {
    sizes: [50, 50],
  });
}

window.initMap = initMap;
index.js

Note: The JavaScript is compiled from the TypeScript snippet.

CSS

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
#map {
  height: 100%;
}

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

#container,
#left,
#right,
.map,
.gutter {
  height: 100%;
}

#left,
#right,
.gutter {
  float: left;
  position: relative;
  overflow: hidden;
}

#map-left {
  position: absolute;
  left: 0;
  top: 0;
}

#map-right {
  position: absolute;
  right: 0;
  top: 0;
}

.gutter {
  background-color: #eee;
  background-repeat: no-repeat;
  background-position: 50%;
}

.gutter.gutter-horizontal {
  cursor: col-resize;
  background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAeCAYAAADkftS9AAAAIklEQVQoU2M4c+bMfxAGAgYYmwGrIIiDjrELjpo5aiZeMwF+yNnOs5KSvgAAAABJRU5ErkJggg==");
}
style.css

HTML

<html>
  <head>
    <title>Split Map Panes</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/split.js/1.5.11/split.min.js"></script>

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <div id="container">
      <div id="left">
        <div id="map-left" class="map"></div>
      </div>
      <div id="right">
        <div id="map-right" class="map"></div>
      </div>
    </div>

    <!-- 
      The `defer` attribute causes the callback 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=initMap&v=weekly"
      defer
    ></script>
  </body>
</html>
index.html

Try Sample

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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-split-map-panes 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