I'm trying to debug an error message in a large and plicated frames based web/ASP.Net app using IE8 and Visual Studio 2010. Specifically, I am getting a "Member not found" message box which appears to be a straightforward JavaScript alert(). Unfortunately I don't know where in the code the problem is happening, and fiddler2 wasn't much help in this case.

My question is, can I get IE to break at the alert() call so that I can debug it?

I'm trying to debug an error message in a large and plicated frames based web/ASP.Net app using IE8 and Visual Studio 2010. Specifically, I am getting a "Member not found" message box which appears to be a straightforward JavaScript alert(). Unfortunately I don't know where in the code the problem is happening, and fiddler2 wasn't much help in this case.

My question is, can I get IE to break at the alert() call so that I can debug it?

• javascript
• debugging
• internet-explorer-8

Share Improve this question Follow edited Aug 22, 2019 at 13:15 Stephen Kennedy asked Jul 1, 2011 at 16:12 Stephen KennedyStephen Kennedy 21.6k2424 gold badges9797 silver badges113113 bronze badges

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6 Answers 6

Sorted by: Reset to default 5

String search for "Member not found"

Add 1 / 0; before the line.

Turn on break on all errors.

(I assumed you knew the developer tool existed. Hit F12 and navigate to the script tab)

Edit:

Thanks to @DmitriyNaumov

var aalert = window.alert;
window.alert = function() {
  aalert.apply(this, arguments);
  1 / 0;
}

You can try using the IE Developer Toolbar from Microsoft. I don't know if it allows you to Set JS breakpoints, but it is a great tool to have on hand anyway!

You can use the IE debugger , press F12 and then under the script tab you can add breakpoints

Using IE 8 you can use Developer Tools which is a little like Firebug for Mozilla Firefox.

http://www.microsoft./download/en/details.aspx?id=18359

(for more information)

this way you can create breakpoints and debug the script execution on the page step by step

Just press F12

Change alert into a new function that throws a proper error.

window.alert = function(msg) {
  throw "Alert: " + msg;
};

Older versions of IE don't allow overwriting window properties like alert in this way in JavaScript ... but you can still do it with VBScript.

Sub alert(msg)
  Err.Raise 8, "Alert", msg
End Sub

If you go the VBScript route, make sure it precedes any JavaScript that references the alert function, or you'll have missed your opportunity.

If it's a window.alert, you can do this:

1. Enable external debuggers in IE.
2. Attach visual studio as a script debugger.
3. Reproduce the problem.
4. While the alert box is shown, break in the debugger.
5. When you dismiss the alert, the debugger will be paused on the next line of code.
6. Use the current call stack to set a breakpoint where ever before the call will be most useful for the next time.

Unfortunately this trick only applies to alert and confirm, since they are modal dialogs.