How can I get a Javascript stack trace when I throw an exception?

Question

If I throw a Javascript exception myself (eg, throw "AArrggg"), how can I get the stack trace (in Firebug or otherwise)? Right now I just get the message.

edit: As many people below have posted, it is possible to get a stack trace for a JavaScript exception but I want to get a stack trace for my exceptions. For example:

function foo() {
    bar(2);
}
function bar(n) {
    if (n < 2)
        throw "Oh no! 'n' is too small!"
    bar(n-1);
}

When foo is called, I want to get a stack trace which includes the calls to foo, bar, bar.

Answer 1

I don't think there's anything built in that you can use however I did find lots of examples of people rolling their own.

• DIY javascript stack trace
• A Javascript stacktrace in any browser

Answer 2

It is easier to get a stack trace on Firefox than it is on IE but fundamentally here is what you want to do:

Wrap the "problematic" piece of code in a try/catch block:

try {
    // some code that doesn't work
    var t = null;
    var n = t.not_a_value;
}
    catch(e) {
}

If you will examine the contents of the "error" object it contains the following fields:

e.fileName : The source file / page where the issue came from e.lineNumber : The line number in the file/page where the issue arose e.message : A simple message describing what type of error took place e.name : The type of error that took place, in the example above it should be 'TypeError' e.stack : Contains the stack trace that caused the exception

I hope this helps you out.

Answer 3

This snippet may somewhat help, although I didn't try it yet.

Answer 4

You can access the stack (stacktrace in Opera) properties of an Error instance even if you threw it. The thing is, you need to make sure you use throw new Error(string) (don't forget the new instead of throw string.

Example:

try {
    0++;
} catch (e) {
    var myStackTrace = e.stack || e.stacktrace || "";
}