add
Provide a list of DirectionsRoutes, the primary route will default to the first routein the directions route list. All other routes in the list will be drawn on the map using thealternative route style. The routes passed to this method will replace any previously addedroutes. Passing an empty list will clear the routes.
Parameters
directionsRoutes
a list of direction routes, first one being the primary and the rest ofthe routes are considered alternatives.