googlemaps api如何在起点和目的地之间绘制多条路线？

<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap" async defer></script>

function initMap() {
  var directionsService = new google.maps.DirectionsService();
  var directionsRenderer = new google.maps.DirectionsRenderer();
  var map = new google.maps.Map(document.getElementById("map"), {
    center: { lat: 37.7749, lng: -122.4194 },
    zoom: 12,
  });
  directionsRenderer.setMap(map);
}

var request = {
  origin: "起点地址或经纬度",
  destination: "目的地地址或经纬度",
  travelMode: google.maps.TravelMode.DRIVING, // 交通方式，可以是DRIVING（驾车）、WALKING（步行）、BICYCLING（骑车）或TRANSIT（公共交通）
};

directionsService.route(request, function (result, status) {
  if (status == google.maps.DirectionsStatus.OK) {
    directionsRenderer.setDirections(result);
  }
});