1

We just enabled Azure Application Insights for our ASP.Net web application. The site is hosted through Windows Server 2012 VM on IIS 8 in Azure. We enabled client side telemetry to detect browser errors on the client side. We've seen a bunch of these errors pop up:

"Invalid character"
"Invalid character at window.onerror"
Call Stack:
window.onerror@https://www.mywebsite.com/login/:79:32

Our website doesn't get a ton of traffic but this error has been recorded over 400 times in the last 24 hours.

The last two characters :79:32 vary a bit between errors but they always end in :32. I'm guessing these are ASCII characters, but I do not know why these errors showing up. Also, the URL path isn't always the same which means it is happening on more than just our 'login' page.

Azure Insights DOES indicate that ALL clients experiencing this error are using Internet Explorer 11.

I verified that our web application doesn't call window.onerror anywhere.

So my question is, should I be concerned about this error? Is it some kind of compatibility with IE11?

Nathan Thompson
  • 21
  • 6

1 Answers1

1

You are right, it is just some kind of compatibility issue with IE11.
Window.onerror has been available in browsers for some time, even we can find it in browsers as old as IE6 and Firefox2. However, the problem is that every browser implements windows.onerror differently, particularly in how many arguments are sent to the onerror listener and the structure of those arguments, which cause a similar error with yours.
Please refer to the following link.
https://dzone.com/articles/capture-and-report-javascript-errors-with-windowon
Now that we have known that certain Javascript is not compatible with some kind of old browser, I think this is not the problem we concern about. It is just an error that occurred on the client-side, not affecting the operation of the application.

Abraham Qian
  • 7,117
  • 1
  • 8
  • 22