ArcGIS ClosestFacilityParameters how to set id to get the best route

[Storylm]

How do I determine which id the line is from the obtained route?
document API: https://developers.arcgis.com/javascript/latest/api-reference/esri-rest-support-ClosestFacilityParameters.html

        const facilities = [
          {
            id: "a",
            center: [-122.67484, 45.52087],
          },
          {
            id: "b",
            center: [-122.68365, 45.52327],
          },
          {
            id: "c",
            center: [-122.66406, 45.52378],
          },
          {
            id: "d",
            center: [-122.6631, 45.52093],
          },
          {
            id: "e",
            center: [-122.66208, 45.5197],
          },
          {
            id: "f",
            center: [-122.66247, 45.51845],
          },
          {
            id: "g",
            center: [-122.66299, 45.51827],
          },
        ];