There are a few libraries, but I didn't used any of these in big projects, so you might want to try them out:

However, I think it's something simple enough that you might give it a try yourself. I personally did exactly this when I needed to do that. You might also create a simple library that suits your needs.

1. Execute JS methods from Objective-C

This is really just one line of code.

NSString *returnvalue = [webView stringByEvaluatingJavaScriptFromString:@"your javascript code string here"];

More details on the official UIWebView Documentation.

2. Execute Objective-C methods from JS

This is unfortunately slightly more complex, because there isn't the same windowScriptObject property (and class) that exists on Mac OSX allowing complete communication between the two.

However, you can easily call from javascript custom-made URLs, like:

window.location = yourscheme://callfunction/parameter1/parameter2?parameter3=value

And intercept it from Objective-C with this:

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType {
   NSURL *URL = [request URL]; 
   if ([[URL scheme] isEqualToString:@"yourscheme"]) {
       // parse the rest of the URL object and execute functions
   } 
}

This is not as clean as it should be (or by using windowScriptObject) but it works.

3. Listen to native JS events from Objective-C (for example DOM ready event)

From the above explanation, you see that if you want to do that, you have to create some JavaScript code, attach it to the event you want to monitor and call the correct window.location call to be then intercepted.

Again, not clean as it should be, but it works.