在WKWebView中加载网站后，如何检测元素何时可见？

I am trying to load a transit website so I can scrape the stop times for a given stop. After I load the url, the stop times are loaded in a bit later dynamically through javascript. My goal is to detect the presence of elements with a class of "stop-time". If these elements are present in the html I can then parse the html. But before I can parse the html I have to wait for these elements with class of "stop-time" to appear. I read through a bunch of other SO questions but I couldn't quite piece it together. I am implementing the didReceive message function but I'm not really sure how to load in the javascript I need to detect the presence of the elements (elements with class of "stop-time"). I successfully injected some javascript to prevent the location permission popup from showing.I am trying to load a transit website so I can