How to hang a callback for rendering routes in Google Maps?

Question

JavaScript

Hello.
I believe that the rendering of routes in Google maps is asynchronous, so I ran into the following problem: if you quickly clear the routes, and then draw, then complete chaos occurs. Those routes are drawn that do not need to be drawn by condition in js and vice versa, and without any logic. A sequence of asynchronous route renderings will solve this problem, but I don’t understand how to hang up a callback on new google.maps.Polyline(). Perhaps someone knows, or knows how to build a chain of asynchronous renderings for Google maps? Thank you!