Trace Route using Maps API Javascript V3

traceRouteMap.js

function traceRouteMap() {
    var mapElement = document.getElementById('google-map');
    var directionsService = new google.maps.DirectionsService();
    var startLatLng = new google.maps.LatLng(-29.687306,-53.815477);
    var directionsDisplay= new google.maps.DirectionsRenderer();
    var geocoder = new google.maps.Geocoder();
    var markers = [];
    var center;
    var mapOptions = {
        zoom: 12,
        center: startLatLng,
        scrollwheel: false
    };
    var map = new google.maps.Map(mapElement, mapOptions);
    directionsDisplay.setMap(map);
    directionsDisplay.setOptions({ suppressMarkers: true });
    var marker = new google.maps.Marker({
        map: map,
        draggable: false,
        animation: google.maps.Animation.DROP,
        position: startLatLng,
        icon: "/static/images/pin_map.png"
    });

    //Add marker to Push Array to count after route show
    markers.push(marker);

    //Trigger Form Submit
    $('#google-form').on('submit', function() {
        event.preventDefault();
        var address = $('#google-address').val();

        //Get LatLng based on address entered
        geocoder.geocode( { 'address': address}, function(results, status) {
            //If get LatLng based on address
            if (results.length) {
                var request = {
                    origin      : results[0].geometry.location,
                    destination : startLatLng,
                    travelMode  : google.maps.TravelMode.DRIVING
                };
                directionsService.route(request, function(result, status) {
                    // IF OK and have Route to show
                    if (status == google.maps.DirectionsStatus.OK) {
                        directionsDisplay.setDirections(result);
                        if(markers.length > 1) {
                            markers[1].setMap(null);
                            markers.splice(1,1);
                        }
                        var marker2 = new google.maps.Marker({
                            position: result.routes[0].legs[0].start_location,
                            map: map,
                            icon: '/static/images/pin_map.png'
                        });
                        markers.push(marker2);
                        $('.retorno-mapa').html('');
                    } else {
                        $('.retorno-mapa').html('Não foi possível montar um trajeto.');
                    }
                });

            } else {
                $('.retorno-mapa').html('Ocorreu um problema, reveja seu endereço ou tente novamente.');
            }
        });
        return false;
    });


    google.maps.event.addDomListener(window, "resize", function() {
        var center = map.getCenter();
        google.maps.event.trigger(map, "resize");
        map.setCenter(center);
    });

}

function loadScript(callBack) {
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = 'https://maps.googleapis.com/maps/api/js?v=3.exp' +
        '&signed_in=true&language=pt-BR&callback='+callBack;
    document.body.appendChild(script);
}


if($('#google-map').length) {
    window.onload = loadScript('traceRouteMap');
}