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Encoding methods

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JavaScript
function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 14,
    center: {lat: 34.366, lng: -89.519}
  });
  var poly = new google.maps.Polyline({
    strokeColor: '#000000',
    strokeOpacity: 1,
    strokeWeight: 3,
    map: map
  });

  // Add a listener for the click event
  google.maps.event.addListener(map, 'click', function(event) {
    addLatLngToPoly(event.latLng, poly);
  });
}

/**
 * Handles click events on a map, and adds a new point to the Polyline.
 * Updates the encoding text area with the path's encoded values.
 */
function addLatLngToPoly(latLng, poly) {
  var path = poly.getPath();
  // Because path is an MVCArray, we can simply append a new coordinate
  // and it will automatically appear
  path.push(latLng);

  // Update the text field to display the polyline encodings
  var encodeString = google.maps.geometry.encoding.encodePath(path);
  if (encodeString) {
    document.getElementById('encoded-polyline').value = encodeString;
  }
}
JavaScript + HTML
<!DOCTYPE html>
<html>
  <head>
    <title>Encoding methods</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <style>
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
      #map {
        height: 100%;
      }
#panel {
  position: absolute;
  top: 10px;
  left: 25%;
  z-index: 5;
  background-color: #fff;
  padding: 5px;
  border: 1px solid #999;
  text-align: center;
}

/**
 * Provide the following styles for both ID and class, where ID represents an
 * actual existing "panel" with JS bound to its name, and the class is just
 * non-map content that may already have a different ID with JS bound to its
 * name.
 */

#panel, .panel {
  font-family: 'Roboto','sans-serif';
  line-height: 30px;
  padding-left: 10px;
}

#panel select, #panel input, .panel select, .panel input {
  font-size: 15px;
}

#panel select, .panel select {
  width: 100%;
}

#panel i, .panel i {
  font-size: 12px;
}

    </style>
  </head>
  <body>
    <div id="map" style="width: 50%; float:left"></div>
    <div style="width:46%; float:left" class="panel">
      <div>Encoding:</div>
      <textarea id="encoded-polyline" style="height: 100px; width: 100%"></textarea>
    </div>
    <script>
function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 14,
    center: {lat: 34.366, lng: -89.519}
  });
  var poly = new google.maps.Polyline({
    strokeColor: '#000000',
    strokeOpacity: 1,
    strokeWeight: 3,
    map: map
  });

  // Add a listener for the click event
  google.maps.event.addListener(map, 'click', function(event) {
    addLatLngToPoly(event.latLng, poly);
  });
}

/**
 * Handles click events on a map, and adds a new point to the Polyline.
 * Updates the encoding text area with the path's encoded values.
 */
function addLatLngToPoly(latLng, poly) {
  var path = poly.getPath();
  // Because path is an MVCArray, we can simply append a new coordinate
  // and it will automatically appear
  path.push(latLng);

  // Update the text field to display the polyline encodings
  var encodeString = google.maps.geometry.encoding.encodePath(path);
  if (encodeString) {
    document.getElementById('encoded-polyline').value = encodeString;
  }
}

    </script>
    <script src="https://maps.googleapis.com/maps/api/js?signed_in=true&libraries=geometry&callback=initMap"
        async defer></script>
  </body>
</html>

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