How can my iPhone Objective-C code get notified of Javascript errors in a UIWebView?

Question

I need to have my iPhone Objective-C code catch Javascript errors in a UIWebView. That includes uncaught exceptions, syntax errors when loading files, undefined variable re

Answer 1

First setup WebViewJavascriptBridge , then override console.error function.

In javascript

    window.originConsoleError = console.error;
    console.error = (msg) => {
        window.originConsoleError(msg);
        bridge.callHandler("sendConsoleLogToNative", {
            action:action,
            message:message
        }, null)
    };

In Objective-C

[self.bridge registerHandler:@"sendConsoleLogToNative" handler:^(id data, WVJBResponseCallback responseCallback) {
    NSString *action = data[@"action"];
    NSString *msg = data[@"message"];
    if (isStringValid(action)){
        if ([@"console.error" isEqualToString:action]){
            NSLog(@"JS error :%@",msg);
        }
    }
}];

Answer 2

See exception handling in iOS7: http://www.bignerdranch.com/blog/javascriptcore-example/

[context setExceptionHandler:^(JSContext *context, JSValue *value) {
    NSLog(@"%@", value);
}];

Answer 3

A simpler solution for some cases might be to just add Firebug Lite to the Web page.

Answer 4

Straight Forward Way: Put this code on top of your controller/view that is using the UIWebView

#ifdef DEBUG
@interface DebugWebDelegate : NSObject
@end
@implementation DebugWebDelegate
@class WebView;
@class WebScriptCallFrame;
@class WebFrame;
- (void)webView:(WebView *)webView   exceptionWasRaised:(WebScriptCallFrame *)frame
       sourceId:(int)sid
           line:(int)lineno
    forWebFrame:(WebFrame *)webFrame
{
    NSLog(@"NSDD: exception: sid=%d line=%d function=%@, caller=%@, exception=%@", 
          sid, lineno, [frame functionName], [frame caller], [frame exception]);
}
@end
@interface DebugWebView : UIWebView
id windowScriptObject;
id privateWebView;
@end
@implementation DebugWebView
- (void)webView:(id)sender didClearWindowObject:(id)windowObject forFrame:(WebFrame*)frame
{
    [sender setScriptDebugDelegate:[[DebugWebDelegate alloc] init]];
}
@end
#endif

And then instantiate it like this:

#ifdef DEBUG
        myWebview = [[DebugWebView alloc] initWithFrame:frame];
#else
        myWebview = [[UIWebView alloc] initWithFrame:frame];
#endif

Using #ifdef DEBUG ensures that it doesn't go in the release build, but I would also recommend commenting it out when you're not using it since it has a performance impact. Credit goes to Robert Sanders and Prcela for the original code

Also if using ARC you may need to add "-fno-objc-arc" to prevent some build errors.