What thread does the completionHandler of WKWebView's evaluateJavascript method run on?

Question

I am trying to figure out if it is safe to manipulate UI objects in the completion handler of WKWebView's - evaluateJavaScript:completionHandler:. The docs do not seem to specify.

Answer 1

https://developer.apple.com/reference/webkit/wkwebview/1415017-evaluatejavascript?language=objc

The completion handler always runs on the main thread.

Almost at the very end of the page. Possibly added sometime after you posted this question.

Answer 2

It does not matter. If it is not specified then you should assume that it is not.

You can very easily run your UI code on the main thread using:

dispatch_async(dispatch_get_main_queue(), ^{
    // Your UI code here
});

Better safe than sorry.