javascript - How to display alternative route using google map api

Question

I am using google map and i am bit of stuck at one point. i want to display alternative route for my source and destination point. currently i am using the code which is working perfectly and displaying correct result but the only the problem is that this code displaying only single route for my starting and destination path.

Here is my JSFIDDLE WORKING DEMO

Here is sample code which i am using in jsfiddle demo link:

HTML CODE:

<h1>Calculate your route</h1>
<form id="calculate-route" name="calculate-route" action="#" method="get">
  <label for="from">From:</label>
  <input type="text" id="from" name="from" required="required" placeholder="An address" size="30" />
  <a id="from-link" href="#">Get my position</a>
  <br />

  <label for="to">To:</label>
  <input type="text" id="to" name="to" required="required" placeholder="Another address" size="30" />
  <a id="to-link" href="#">Get my position</a>
  <br />

  <input type="submit" />
  <input type="reset" />
</form>  

JS CODE:

<script>
  function calculateRoute(from, to) {
    // Center initialized to Naples, Italy
    var myOptions = {
      zoom: 10,
      center: new google.maps.LatLng(40.84, 14.25),
      mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    // Draw the map
    var mapObject = new google.maps.Map(document.getElementById("map"), myOptions);

    var directionsService = new google.maps.DirectionsService();
    var directionsRequest = {
      origin: from,
      destination: to,
      provideRouteAlternatives: true,
      travelMode: google.maps.DirectionsTravelMode.DRIVING,
      unitSystem: google.maps.UnitSystem.METRIC
    };
    directionsService.route(
      directionsRequest,
      function(response, status)
      {
        if (status == google.maps.DirectionsStatus.OK)
        {
          new google.maps.DirectionsRenderer({
            map: mapObject,
            directions: response
          });
        }
        else
          $("#error").append("Unable to retrieve your route<br />");
      }
    );
  }

  $(document).ready(function() {
    // If the browser supports the Geolocation API
    if (typeof navigator.geolocation == "undefined") {
      $("#error").text("Your browser doesn't support the Geolocation API");
      return;
    }

    $("#from-link, #to-link").click(function(event) {
      event.preventDefault();
      var addressId = this.id.substring(0, this.id.indexOf("-"));

      navigator.geolocation.getCurrentPosition(function(position) {
        var geocoder = new google.maps.Geocoder();
        geocoder.geocode({
          "location": new google.maps.LatLng(position.coords.latitude, position.coords.longitude)
        },
        function(results, status) {
          if (status == google.maps.GeocoderStatus.OK)
            $("#" + addressId).val(results[0].formatted_address);
          else
            $("#error").append("Unable to retrieve your address<br />");
        });
      },
      function(positionError){
        $("#error").append("Error: " + positionError.message + "<br />");
      },
      {
        enableHighAccuracy: true,
        timeout: 10 * 1000 // 10 seconds
      });
    });

    $("#calculate-route").submit(function(event) {
      event.preventDefault();
      calculateRoute($("#from").val(), $("#to").val());
    });
  });
</script>

you can see in the demo when you enter starting point and destination point it will give you single route accordingly but i need to display alternative route as well in the map.

Is there any way we can choose and display a route between the given options according to the 'distance' or the 'duration in traffic'?

Thanks in advance for your help and much appreciated

Answer 1

What you need to do is check how many routes are returned by the directionsService.route function call, within the callback function which receives the response object response.routes will be an array, so loop through it and use the loop counter to set the routeIndex for the DirectionsRenderer to use. Of course this resulting output is not at all in my opinion desirable, as very often segments of alternative routes will overlap so it won't always be visually obvious to a user whats going on with the other extra lines. As well as if you actually display the text directions, will need different DOM element for display of each set of directions, and then it's confusing too which set is for what. I would rather advise showing the main (first) route only and having buttons to display alternatives which upon clicking would show only those routes & directions. That said, here is the fix for your question:

directionsService.route(
    directionsRequest,
    function (response, status) {
        if (status == google.maps.DirectionsStatus.OK) {
            for (var i = 0, len = response.routes.length; i < len; i++) {
                new google.maps.DirectionsRenderer({
                    map: mapObject,
                    directions: response,
                    routeIndex: i
                });
            }
        } else {
            $("#error").append("Unable to retrieve your route<br />");
        }
    }
);