Is it possible to prevent JavaScript alert|confirm|prompt from popping up in UIWebView before the rendering process is finished?

Question

Is it possible to prevent JavaScript alert|confirm|prompt from popping up in UIWebView before the rendering process is finished?

Several questions have been asked on SO regarding similar issues, but none have addressed my specific question. Many of the answers suggest running a JS snippet that overloads the alert method, like this: window.alert = function() {};

The issue I am facing is that a webpage (whose content I cannot control) triggers an alert before the entire page has finished rendering.

Due to this, I am unable to utilize the

- (void)webViewDidFinishLoad:(UIWebView *)webView

delegate method to execute the JS snippet. Running the snippet in

- (void)webViewDidStartLoad:(UIWebView *)webView

also doesn't help because it runs before the DOM is loaded.

Answer №1

After testing different methods for injecting Javascript, I decided to go back to using the native platform.

By utilizing a UIWebView, which automatically converts Javascript alerts into native UIAlertViews, I was able to easily block them on the native side. By examining UIAlertView.h, I found that there is only one public method for displaying an alert, appropriately named: - (void)show;.

To achieve this, I created a category in order to avoid potential issues with subclassing UIAlertView as mentioned in the documentation.

@interface UIAlertView (Blocker)
@end

#import "UIAlertView+Blocker.h"

@implementation UIAlertView (Blocker)

- (void)show {
   return;
}
@end

By importing this category into the view controller containing the UIWebView, all instances of UIAlertView and consequently all JS alerts are blocked.

I believe this solution is more reliable as it does not involve manipulating Javascript, altering HTML, or relying on external libraries. It is also not dependent on where the JS-alert code is located within the web content.

Answer 2

After testing different methods for injecting Javascript, I decided to go back to using the native platform.

By utilizing a UIWebView, which automatically converts Javascript alerts into native UIAlertViews, I was able to easily block them on the native side. By examining UIAlertView.h, I found that there is only one public method for displaying an alert, appropriately named: - (void)show;.

To achieve this, I created a category in order to avoid potential issues with subclassing UIAlertView as mentioned in the documentation.

@interface UIAlertView (Blocker)
@end

#import "UIAlertView+Blocker.h"

@implementation UIAlertView (Blocker)

- (void)show {
   return;
}
@end

By importing this category into the view controller containing the UIWebView, all instances of UIAlertView and consequently all JS alerts are blocked.

I believe this solution is more reliable as it does not involve manipulating Javascript, altering HTML, or relying on external libraries. It is also not dependent on where the JS-alert code is located within the web content.

Answer 3

Answer №2

It appears that the outcome could differ depending on the rendering engine being used. In my experience, the following approach seemed to be effective:

alert("something");
alert = function(){};
alert("awesome");

http://jsfiddle.net/g5S5M/ I am aware of the differences in engines such as V8 used by Chrome compared to Firefox or IE. Therefore, when developing complex web applications, careful consideration is needed as browsers may interpret JavaScript differently.

Consider looking into third-party libraries that might override this function. If you encounter conflicts where one script makes alert blank and another reinstates it, you may need to remove or adjust the library or alter their execution order.

Answer 4

It appears that the outcome could differ depending on the rendering engine being used. In my experience, the following approach seemed to be effective:

alert("something");
alert = function(){};
alert("awesome");

http://jsfiddle.net/g5S5M/ I am aware of the differences in engines such as V8 used by Chrome compared to Firefox or IE. Therefore, when developing complex web applications, careful consideration is needed as browsers may interpret JavaScript differently.

Consider looking into third-party libraries that might override this function. If you encounter conflicts where one script makes alert blank and another reinstates it, you may need to remove or adjust the library or alter their execution order.

Is it possible to prevent JavaScript alert|confirm|prompt from popping up in UIWebView before the rendering process is finished?

Answer №1

Answer №2

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