An issue while showing a path on Google Maps

Question

I have multiple points of longitude and latitude. For example:

1 long lat, starting point   
2 long lat   
3 long lat     
4 long lat
.
.
.

. <

Answer 1

Don't push the src into the path, it is a duplicate of the first point in the overview path. Remove this line:

path.push(src);

working fiddle

code snippet:

var markers = [{
    "title": '1',
    "lat": '30.705911',
    "lng": '76.679656',
    "description": '1'
  }, {
    "title": '2',
    "lat": '30.701713',
    "lng": '76.684097',
    "description": '2'
  }, {
    "title": '2',
    "lat": '30.703291',
    "lng": ' 76.701022',
    "description": '2'
  }, {
    "title": '2',
    "lat": '30.691888',
    "lng": ' 76.710721',
    "description": '2'
  }

];
window.onload = function() {
  var mapOptions = {
    center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
    zoom: 10,
    mapTypeId: google.maps.MapTypeId.ROADMAP
  };
  var map = new google.maps.Map(document.getElementById("dvMap"), mapOptions);
  var infoWindow = new google.maps.InfoWindow();
  var lat_lng = new Array();
  var latlngbounds = new google.maps.LatLngBounds();
  for (i = 0; i < markers.length; i++) {
    var data = markers[i]
    var myLatlng = new google.maps.LatLng(data.lat, data.lng);
    lat_lng.push(myLatlng);
    var marker = new google.maps.Marker({
      position: myLatlng,
      map: map,
      title: data.title
    });
    latlngbounds.extend(marker.position);
    (function(marker, data) {
      google.maps.event.addListener(marker, "click", function(e) {
        infoWindow.setContent(data.description);
        infoWindow.open(map, marker);
      });
    })(marker, data);
  }
  map.setCenter(latlngbounds.getCenter());
  map.fitBounds(latlngbounds);

  //***********ROUTING****************//

  //Intialize the Path Array
  var path = new google.maps.MVCArray();

  //Intialize the Direction Service
  var service = new google.maps.DirectionsService();

  //Set the Path Stroke Color
  var poly = new google.maps.Polyline({
    map: map,
    strokeColor: '#4986E7'
  });

  //Loop and Draw Path Route between the Points on MAP
  for (var i = 0; i < lat_lng.length; i++) {
    if ((i + 1) < lat_lng.length) {
      var src = lat_lng[i];
      var des = lat_lng[i + 1];
      // path.push(src);
      poly.setPath(path);
      service.route({
        origin: src,
        destination: des,
        travelMode: google.maps.DirectionsTravelMode.DRIVING
      }, function(result, status) {
        if (status == google.maps.DirectionsStatus.OK) {
          for (var i = 0, len = result.routes[0].overview_path.length; i < len; i++) {
            path.push(result.routes[0].overview_path[i]);
          }
        }
      });
    }
  }
}

html,
body,
#dvMap {
  height: 100%;
  width: 100%;
  margin: 0px;
  padding: 0px
}

<script src="http://maps.google.com/maps/api/js"></script>
<div id="dvMap" ></div>