Getting Lat/Lng from a Click Event

This example listens for the click event, gets the latitude and longitude coordinates of the click from google.maps.MouseEvent.latLng, and displays those coordinates in an info window.

Read the documentation.

function initMap() {
  var myLatlng = {lat: -25.363, lng: 131.044};

  var map = new google.maps.Map(
      document.getElementById('map'), {zoom: 4, center: myLatlng});

  // Create the initial InfoWindow.
  var infoWindow = new google.maps.InfoWindow(
      {content: 'Click the map to get Lat/Lng!', position: myLatlng});
  infoWindow.open(map);

  // Configure the click listener.
  map.addListener('click', function(mapsMouseEvent) {
    // Close the current InfoWindow.
    infoWindow.close();

    // Create a new InfoWindow.
    infoWindow = new google.maps.InfoWindow({position: mapsMouseEvent.latLng});
    infoWindow.setContent(mapsMouseEvent.latLng.toString());
    infoWindow.open(map);
  });
}
<div id="map"></div>
/* 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;
}
<!-- Replace the value of the key parameter with your own API key. -->
<script async defer
src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initMap">
</script>

Try it yourself

You can experiment with this code in JSFiddle by clicking the <> icon in the top-right corner of the code window.

<!DOCTYPE html>
<html>
  <head>
    <title>Getting LatLng from a Click Event</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <style>
      /* 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;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script>
      function initMap() {
        var myLatlng = {lat: -25.363, lng: 131.044};

        var map = new google.maps.Map(
            document.getElementById('map'), {zoom: 4, center: myLatlng});

        // Create the initial InfoWindow.
        var infoWindow = new google.maps.InfoWindow(
            {content: 'Click the map to get Lat/Lng!', position: myLatlng});
        infoWindow.open(map);

        // Configure the click listener.
        map.addListener('click', function(mapsMouseEvent) {
          // Close the current InfoWindow.
          infoWindow.close();

          // Create a new InfoWindow.
          infoWindow = new google.maps.InfoWindow({position: mapsMouseEvent.latLng});
          infoWindow.setContent(mapsMouseEvent.latLng.toString());
          infoWindow.open(map);
        });
      }
    </script>
    <script async defer
    src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap">
    </script>
  </body>
</html>