Google Maps – Dev-Notes

December 31, 2012June 26, 2018

Google Maps with input events

This example code updates a set of input fields with latitude-longitude values in response to mouse clicks on an instance of Google Maps. It can also redraw map markers upon typing in new coordinates.


<html>
  <head>
    <style type="text/css">
      html { height: 100% }
      body { height: 100%; margin: 10; padding: 10 }
      #map_canvas { height: 100% }
    </style>
    <script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?sensor=true"></script>
    <script type="text/javascript">
      var map;
      var currMarker = new google.maps.Marker();

      function initialize() {
        var myLatLng = new google.maps.LatLng(0, 0);
        var mapOptions = {
          center: myLatLng,
          zoom: 1,
          mapTypeId: google.maps.MapTypeId.ROADMAP
        };
        map = new google.maps.Map(document.getElementById("map_canvas"),
            mapOptions);

        google.maps.event.addListener(map, 'click', function(event) {
          placeMarker(event.latLng);
        });
      }

      function placeMarker(location) {
        currMarker.setMap(null);
        var marker = new google.maps.Marker({
            position: location,
            map: map
        });    
        currMarker=marker;

        document.getElementById("lat").value=location.lat();
        document.getElementById("lng").value=location.lng();
      }

      function updateMarker() {
        currMarker.setMap(null);
        var lat = document.getElementById("lat").value;
        var lng = document.getElementById("lng").value;
        var newLatLng = new google.maps.LatLng(lat, lng);
        var marker = new google.maps.Marker({
            position: newLatLng,
            map: map
        });    
        currMarker=marker;
      }
    </script>
  </head>
  <body onload="initialize()">
  <p>
    <div id="map_canvas" style="width:400px; height:400px"></div>
    <div id="coordinates">
      lat: <input id="lat" type="text" onchange="updateMarker()" value="0" />
      lng: <input id="lng" type="text" onchange="updateMarker()" value="0" />
    </div>
  </p>
  </body>
</html>

Below is a screenshot of what the code creates: