RCTCustomWebView.m

// RCTCustomWebView.m
#import "RCTCustomWebView.h"
#import "RCTWebView+Custom.h"

@interface RCTCustomWebView ()

@property (nonatomic, copy) RCTDirectEventBlock onNavigationCompleted;

@end

@implementation RCTCustomWebView { }

- (BOOL)webView:(__unused UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request
 navigationType:(UIWebViewNavigationType)navigationType
{
  BOOL allowed = [super webView:webView shouldStartLoadWithRequest:request navigationType:navigationType];
  
  if (allowed) {
    NSString* url = request.URL.absoluteString;
    if (url && [url isEqualToString:_finalUrl]) {
      if (_onNavigationCompleted) {
        NSMutableDictionary<NSString *, id> *event = [self baseEvent];
        _onNavigationCompleted(event);
      }
    }
  }
  
  return allowed;
}

@end