function calculateAndDisplayRoute(directionsService, directionsRenderer) {
var waypts = [];
var checkboxArray = document.getElementById('waypoints');
for (var i = 0; i < checkboxArray.length; i++) {
if (checkboxArray.options[i].selected) {
waypts.push({
location: checkboxArray[i].value,
stopover: true
});
}
}
directionsService.route({
origin: document.getElementById('start').value,
destination: document.getElementById('end').value,
waypoints: waypts,
optimizeWaypoints: true,
travelMode: 'DRIVING'
}, function(response, status) {
if (status === 'OK') {
directionsRenderer.setDirections(response);
var route = response.routes[0];
var summaryPanel = document.getElementById('directions-panel');
summaryPanel.innerHTML = '';
// For each route, display summary information.
for (var i = 0; i < route.legs.length; i++) {
var routeSegment = i + 1;
summaryPanel.innerHTML += '<b>Route Segment: ' + routeSegment +
'</b><br>';
summaryPanel.innerHTML += route.legs[i].start_address + ' to ';
summaryPanel.innerHTML += route.legs[i].end_address + '<br>';
summaryPanel.innerHTML += route.legs[i].distance.text + '<br><br>';
}
} else {
window.alert('Directions request failed due to ' + status);
}
});
}
</script>
<script async defer
src="https://maps.googleapis.com/maps/api/js?key=AIzaSyAzEvU4pM-dnHNJz4TScnB2C2lkf7TIXlE&callback=initMap">
</script>
</body>
</html>