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

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

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.

Solutions/Answers:

Solution 1:

Edit 2 (2017):

In all modern browsers you can simply call: console.trace(); (MDN Reference)

Edit 1 (2013):

A better (and simpler) solution as pointed out in the comments on the original question is to use the stack property of an Error object like so:

function stackTrace() {
    var err = new Error();
    return err.stack;
}

This will generate output like this:

DBX.Utils.stackTrace@http://localhost:49573/assets/js/scripts.js:44
DBX.Console.Debug@http://localhost:49573/assets/js/scripts.js:9
.success@http://localhost:49573/:462
x.Callbacks/c@http://localhost:49573/assets/js/jquery-1.10.2.min.js:4
x.Callbacks/p.fireWith@http://localhost:49573/assets/js/jquery-1.10.2.min.js:4
k@http://localhost:49573/assets/js/jquery-1.10.2.min.js:6
.send/r@http://localhost:49573/assets/js/jquery-1.10.2.min.js:6

Giving the name of the calling function along with the URL, its calling function, and so on.

Original (2009):

A modified version of this snippet may somewhat help:

function stacktrace() { 
  function st2(f) {
    return !f ? [] : 
        st2(f.caller).concat([f.toString().split('(')[0].substring(9) + '(' + f.arguments.join(',') + ')']);
  }
  return st2(arguments.callee.caller);
}

Solution 2:

Note that chromium/chrome (other browsers using V8), and also Firefox do have a convenient interface to get a stacktrace through a stack property on Error objects.

try {
   // Code throwing an exception
} catch(e) {
  console.log(e.stack);
}

It applies for the base exceptions as well as for the ones you throw yourself. (Considered that you use the Error class, which is anyway a good practice).

See details on V8 documentation

Solution 3:

In Firefox it seems that you don’t need to throw the exception. It’s sufficient to do

e = new Error();
console.log(e.stack);

Solution 4:

If you have firebug, there’s a break on all errors option in the script tab. Once the script has hit your breakpoint, you can look at firebug’s stack window:

screenshot

Solution 5:

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.

Solution 6:

A good (and simple) solution as pointed out in the comments on the original question is to use the stack property of an Error object like so:

function stackTrace() {
    var err = new Error();
    return err.stack;
}

This will generate output like this:

DBX.Utils.stackTrace@http://localhost:49573/assets/js/scripts.js:44
DBX.Console.Debug@http://localhost:49573/assets/js/scripts.js:9
.success@http://localhost:49573/:462
x.Callbacks/c@http://localhost:49573/assets/js/jquery-1.10.2.min.js:4
x.Callbacks/p.fireWith@http://localhost:49573/assets/js/jquery-1.10.2.min.js:4
k@http://localhost:49573/assets/js/jquery-1.10.2.min.js:6
.send/r@http://localhost:49573/assets/js/jquery-1.10.2.min.js:6

Giving the name of the calling function along with the URL and line number, its calling function, and so on.

I have a really elaborate and pretty solution that I have devised for a project I am currently working on and I have extracted and reworked it a bit to be generalized. Here it is:

(function(context){
    // Only global namespace.
    var Console = {
        //Settings
        settings: {
            debug: {
                alwaysShowURL: false,
                enabled: true,
                showInfo: true
            },
            stackTrace: {
                enabled: true,
                collapsed: true,
                ignoreDebugFuncs: true,
                spacing: false
            }
        }
    };

    // String formatting prototype function.
    if (!String.prototype.format) {
        String.prototype.format = function () {
            var s = this.toString(),
                args = typeof arguments[0],
                args = (("string" == args || "number" == args) ? arguments : arguments[0]);
            if (!arguments.length)
                return s;
            for (arg in args)
                s = s.replace(RegExp("\\{" + arg + "\\}", "gi"), args[arg]);
            return s;
        }
    }

    // String repeating prototype function.
    if (!String.prototype.times) {
        String.prototype.times = function () {
            var s = this.toString(),
                tempStr = "",
                times = arguments[0];
            if (!arguments.length)
                return s;
            for (var i = 0; i < times; i++)
                tempStr += s;
            return tempStr;
        }
    }

    // Commonly used functions
    Console.debug = function () {
        if (Console.settings.debug.enabled) {
            var args = ((typeof arguments !== 'undefined') ? Array.prototype.slice.call(arguments, 0) : []),
                sUA = navigator.userAgent,
                currentBrowser = {
                    firefox: /firefox/gi.test(sUA),
                    webkit: /webkit/gi.test(sUA),
                },
                aLines = Console.stackTrace().split("\n"),
                aCurrentLine,
                iCurrIndex = ((currentBrowser.webkit) ? 3 : 2),
                sCssBlack = "color:black;",
                sCssFormat = "color:{0}; font-weight:bold;",
                sLines = "";

            if (currentBrowser.firefox)
                aCurrentLine = aLines[iCurrIndex].replace(/(.*):/, "$1@").split("@");
            else if (currentBrowser.webkit)
                aCurrentLine = aLines[iCurrIndex].replace("at ", "").replace(")", "").replace(/( \()/gi, "@").replace(/(.*):(\d*):(\d*)/, "$1@$2@$3").split("@");

            // Show info if the setting is true and there's no extra trace (would be kind of pointless).
            if (Console.settings.debug.showInfo && !Console.settings.stackTrace.enabled) {
                var sFunc = aCurrentLine[0].trim(),
                    sURL = aCurrentLine[1].trim(),
                    sURL = ((!Console.settings.debug.alwaysShowURL && context.location.href == sURL) ? "this page" : sURL),
                    sLine = aCurrentLine[2].trim(),
                    sCol;

                if (currentBrowser.webkit)
                    sCol = aCurrentLine[3].trim();

                console.info("%cOn line %c{0}%c{1}%c{2}%c of %c{3}%c inside the %c{4}%c function:".format(sLine, ((currentBrowser.webkit) ? ", column " : ""), ((currentBrowser.webkit) ? sCol : ""), sURL, sFunc),
                             sCssBlack, sCssFormat.format("red"),
                             sCssBlack, sCssFormat.format("purple"),
                             sCssBlack, sCssFormat.format("green"),
                             sCssBlack, sCssFormat.format("blue"),
                             sCssBlack);
            }

            // If the setting permits, get rid of the two obvious debug functions (Console.debug and Console.stackTrace).
            if (Console.settings.stackTrace.ignoreDebugFuncs) {
                // In WebKit (Chrome at least), there's an extra line at the top that says "Error" so adjust for this.
                if (currentBrowser.webkit)
                    aLines.shift();
                aLines.shift();
                aLines.shift();
            }

            sLines = aLines.join(((Console.settings.stackTrace.spacing) ? "\n\n" : "\n")).trim();

            trace = typeof trace !== 'undefined' ? trace : true;
            if (typeof console !== "undefined") {
                for (var arg in args)
                    console.debug(args[arg]);

                if (Console.settings.stackTrace.enabled) {
                    var sCss = "color:red; font-weight: bold;",
                        sTitle = "%c Stack Trace" + " ".times(70);

                    if (Console.settings.stackTrace.collapsed)
                        console.groupCollapsed(sTitle, sCss);
                    else
                        console.group(sTitle, sCss);

                    console.debug("%c" + sLines, "color: #666666; font-style: italic;");

                    console.groupEnd();
                }
            }
        }
    }
    Console.stackTrace = function () {
        var err = new Error();
        return err.stack;
    }

    context.Console = Console;
})(window);

Check it out on GitHub (currently v1.2)! You can use it like Console.debug("Whatever"); and it will, depending on the settings in Console, print the output and a stack trace (or just simple info/nothing extra at all). Here’s an example:

Console.js

Make sure to play around with the settings in the Console object! You can add spacing between the lines of the trace and turn it off entirely. Here it is with Console.trace set to false:

No trace

You can even turn off the first bit of info shown (set Console.settings.debug.showInfo to false) or disable debugging entirely (set Console.settings.debug.enabled to false) so you never have to comment out a debug statement again! Just leave them in and this will do nothing.