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Chrome DevTools script blackboxing not working

I am trying to use the new feature of chrome devtools "blackboxing a script".
This Chrome Devtools article lists script blackboxing functionality
What happens when you blackbox a script?
Exceptions thrown from library code will not pause (if Pause on
exceptions is enabled)
Stepping into/out/over bypasses the library code
Event listener breakpoints don't break in library code
The debugger will not pause on any breakpoints set in library code.
The end result is you are debugging your application code instead of third party resources.
I have tried to blackbox the file directly by right clicking the file from source tab and everything goes right the yellow notification shows at the top of file "This script is blackboxed in debugger". Strangely none of the above listed points work, debugger goes through blackboxed script also event listeners reference the blackboxed script. I have also enabled Developer Tools experiments at chrome://flags/
With these options set i thought i would have been ok, i also have the latest chrome at this time 39.0 beta,i have no idea what i'm missing. Did anybody go through this?
Thnx!

I had the same issue. One quick and easy way is to look at your Call Stack. As a for instance, Right-Click on one of the 'jquery' functions and select 'black box' from the menu. Nothing else needed. In this example jquery.js will be step-over from that point on.

In your screenshot, I can see a breakpoint.
If you put a breakpoint, it will always break (except if you deactivate it, of course), even with blackboxing being active.

Had the same issue and used good old
have you tried turning it off and on again?
Go to developer tools settings -> Blackboxing -> Remove all entries one by one + disable Blackbox content scripts
Blackboxed again and after that this works fine.

How to debug infinite loops in Firefox/Firebug?

I have an issue with Firebug in Firefox. While my JavaScript produces an endless loop, a popup in Firefox comes up, which allows to continue the script or terminate it.
In earlier versions of Firefox there was an additional option allowing to debug the script, however it is not appearing anymore in the popup in current versions (I am using Firefox 31.0).
Using this option Firebug should stop somewhere in the JavaScript processed in the endless loop. Most likely this behavior can be again activated in Firebug/Firefox but I do not know where?

While this button is not present in Firefox 31.0, it is there in version 32.0. Though instead of stopping in Firebug it now uses the built-in debugger to debug the script.
Background info:
Before version 2.0 Firebug used Firefox' old debugger API called JSD. In Firefox up to version 31.0 the Debug script button is just displayed when that API is enabled, i.e. when Firebug (1.12.* and earlier) is opened for that page.
The debugger of the built-in devtools and Firebug 2.0 use a new debugger API, so as the button is bound to JSD it is not displayed.
In Firefox 32.0+ the button works together with the new API. Though as Firebug (2.0.*) doesn't hook into the logic for that button, it opens the built-in debugger.

There is currently no way to stop the script execution on hanging scripts. There used to be a button to debug them, though it got removed in Firefox 45.
The enhancement request to re-add it is https://bugzil.la/1157820.
For what it's worth, here's a simple test script creating an infinite loop:
data:text/html,<script>while(true){x=1;}</script>
Edit:
There is still a Debug Script button in the Firefox Developer Edition, though it doesn't seem to work (at least in the tested version 81.0b9) trying it with the simple script above.

How to modify javascript code at run time?

Is there a way to modify JavaScript code while debugging? Visual Studio has "Edit and Continue", and similar hot swapping of code can be done in Java and other languages. Can this be done with JavaScript, and if so, how?

Chrome, Safari, and some other WebKit-based browsers contain a feature in the Web Inspector known as Live Edit. If you go to the Scripts panel and are stopped on a breakpoint (or maybe even if not stopped on a breakpoint — I'm not sure), you can double click on a line and start editing that line. The changes you make will take effect on the script.

With Chrome Developer tools, this is super easy.
Just pop open inspector, click on the scripts tab, select which one you want from the dropdown menu and then you are free to edit the script and add in breakpoints. If you refresh the page, your breakpoints will stay there.
If you watch this talk but Paul Irish, he shows how you can edit a script on the fly
http://paulirish.com/2011/a-re-introduction-to-the-chrome-developer-tools/
also good:
http://blip.tv/jsconf/jsconf2011-paul-irish-5382827

If you're talking about while debugging, it's very easy to modify the running code. In your debugging console, you can enter in Javascript expressions and it will run in the context of the window, which contains all the objects and functions of your code, so you can swap them out by redefining them.

Because JavaScript can modify the DOM the you essentially have to change the JavaScript file, save it and reload. For me, I like IE so I run the webpage in a browser NOT IN DEBUG mode. Then you can change the script files, SAVE them. switch back to the browser and reload (F5) to see your changes. Supposedly IE 11 has this ability (probably like Chrome which is essentially what I am doing, changing saving reloading from what I can tell) but I can't get it to find, let alone open a js file. Super poor UI. I'm guessing the browser to open the file icon is but it is always grayed out.

Is there something like "Firebug for IE" (for debugging JavaScript)?

I'm trying to fix some JavaScript bugs. Firebug makes debugging these issues a lot easier when working in Firefox, but what do you do when the code works fine on Firefox but IE is complaining?

you can also check out the IE Developer Toolbar which isn't a debugger but will help you analyze the contents of your code.
Visual Studio will help with the debugging
Fiddler should help analyse the traffic travelling to and from your browser

You can try Firebug Lite or use Visual Studio to debug the JavaScript.

Since Internet Explorer 8, IE has been shipping with a built-in tool-set for debugging, troubleshooting, and generally helping in development of your pages/applications. You can access these tools by pressing F12 while in the browser.
HTML Tab
The HTML tab will let you peek into the DOM as the browser understands it. As you select elements from the HTML view, their styles will be detailed on the right, with individual rules have the ability to be toggled on and off. You can also modify rules, and determine whether the styles on the element were inherited, or assigned explicitly. Additionally, you can even tell which .css file they originate from.
There is a bit more you can do in the HTML tab, such as review and modify attributes on elements, and even make changes to the layout of the element from within the layout section. Additionally, you can make changes directly to the markup to quickly test out some structural ideas.
Script Tab
For resolving JavaScript issues, you can watch the Console and the Script Tag. If your script stumbles across an a call to an undefined method, you'll be alerted within your console. The console also lets you run arbitrary JavaScript against your page, if you want to toggle items on or off, or try bind a handler to a button.
The Script tab great as well as it will format your JavaScript for you, allow you to insert breakpoints, step in and over code blocks, and watch variables over time.
If you've used Firebug, or even the Webkit Inspector, the F12 Developer Tools in Internet Explorer 8+ should be pretty familiar to you.

Firebug lite doesn't work too well for me. The Developer Toolbar just isn't good enough. There really is no great solution.

Or IE Developer Toolbar

Have a look at DebugBar. License is free for personal use

For the DOM Inspector, try the Internet Explorer Developer Toolbar.
For the Net tab, try Fiddler.
For Javascript debugging, try Visual Web Developer 2008 Express Edition. (Or a higher edition of Visual Studio)
Also, try DebugBar.

Visual Studio 2008 can do JavaScript debugging, you have to go to IE's Tools->Internet Options->Advanced and uncheck 'Disable Script Debugging (Internet Explorer)' in order for the browser to bubble up the errors it detects.
Once you're in Visual Studio you basically have it's entire debugging arsenal at your disposal. It's not as integrated as Firebug, but it is way better than anything we used to have.

i think it is better that you first install the ie core addon in firefox then load the page with ie addon and press f12.
good luck.

Make a bookmark in the favourites bar, and put this address as the URL:
javascript:(function(F,i,r,e,b,u,g,L,I,T,E){if(F.getElementById(b))return;E=F[i+'NS']&&F.documentElement.namespaceURI;E=E?F[i+'NS'](E,'script'):F[i]('script');E[r]('id',b);E[r]('src',I+g+T);E[r](b,u);(F[e]('head')[0]||F[e]('body')[0]).appendChild(E);E=new%20Image;E[r]('src',I+L);})(document,'createElement','setAttribute','getElementsByTagName','FirebugLite','4','firebug-lite.js','releases/lite/latest/skin/xp/sprite.png','https://getfirebug.com/','#startOpened');
Then navigatge to the page you want and click the link. Firebug Lite will/should open up...

The IE8 beta comes with what I think is the IE Developer toolbar, but it seems to be a lot more powerful than the last time I tried the toolbar on IE7

I'm guessing this question was posted before the IE8 final came out, according tho some of the answers.
These days, IE8's inbuilt Developer Tools are great; and while the JS debugging isn't as useful as Visual Studio the Dev Tools in general much better than Firebug in my opinion. Between that and the Compatibility View Browser Mode I can handle all my IE6 development needs.

I found a solution to this problem, you could simply stick this tag to the page you are trying to debug and it will open firebug:
<script type="text/javascript" src="https://getfirebug.com/firebug-lite.js"></script>
Explanation from https://getfirebug.com/firebuglite#Stable

If you're a serious Front-end Developer, give AJAX Edition a test run:
http://www.compuware.com/application-performance-management/ajax-performance-testing.html
It's a free tool that allows users’ to understand what is causing performance and functional-related problems in modern AJAX/web Applications.

In IE, go to MenuBar->Tools
Select Debugger Tools
Hit F12 and enjoy.
It is far from Fire Bug, but suitable for some quick help

There is always a way how to get around this issue, watch the video and you will be able to install firebug in 2 mins.
install firebug on ie
Good luck

"No symbols loaded for the current document" while debugging JavaScript in Visual Studio

I'm working on a .NET 3.5 website, with three projects under one solution. I'm using jQuery in this project. I'd like to use the Visual Studio JavaScript debugger to step through my JavaScript code. If I set a breakpoint in any of the .js files I get a warning that says:
The breakpoint will not currently be hit. No symbols have been loaded for this document.
How do I fix this? I'm guessing that Visual Studio is having some trouble parsing through some of the jQuery code. I will try to replace the minimized version of jQuery.js with the expanded version, but I don't think that will fix it.

I was experiencing the same behavior in Visual Studio 2008, and after spending several minutes trying to get the symbols to load I ended up using a workaround - adding a line with the "debugger;" command in my JavaScript file.
After adding debugger; when you then reload the script in Internet Explorer it'll let you bring up a new instance of the script debugger, and it'll stop on your debugger command let you debug from there.
In this scenario I was already debugging the JavaScript in Firebug, but I wanted to debug against Internet Explorer as well.

Make sure you turn on script debugging in your internet options. And if you think it's on, double check it.

I had the same issue, but I solved it by changing my browser settings in Internet Explorer. Go to menu Tools -> Internet Options, select the Advanced tab, then make sure that both "Disable Script Debugging (Internet Explorer)" and "Disable Script Debugging (Other)" are unchecked.
Also, I needed to set Internet Explorer as my default browser, which is normally set as Firefox. To do that, in Visual Studio just right click on any browseable file in Solution Explorer and select "Browse With..." Select Internet Explorer and click "Set as Default".
I'm not sure if there's a way to get debugging running with other browsers, but it wouldn't surprise me if Visual Studio only plays nice with Internet Explorer.
Also, you may need to do "Attach to process" and add IExplorer.exe to get the debugger to start.

I would suggest using FireBug for JavaScript debugging. Give it a spin :)

I finally found the answer to this I think.
When you attach your debugger to the iexplore.exe process, you need to make sure you select "Script" as one of the debugging choices.
It's the button in a red box here: Screenshot of Select Button in Attach to Process Window
Then on the next screen, choose Script: Screenshot of Select Code Type window
This will warn you that you cannot debug Managed and Script at the same time, but that should be fine because your managed code is your server code and you attach to the web process (aspnet or w3wp) instead.
You'll know you did it right because VS 2008 will load ALL the script documents pertaining to that page (inline stuff, eval stuff, etc.) in Solution Explorer.
You'll have full access to the DOM, the immediate window will work, etc. It's pretty slick.

One other thing you might look for is a syntax error in your JavaScript code. That is what happened to me today. No symbols would load because I had one too many parentheses in my code. The IntelliSense barely registered the error. Once I fixed the syntax error, everything worked normally.

All of these answers are correct, but there is one more thing to check. Until yesterday I was always able to debug my JavaScript code from inside of Visual Studio (2012). I had added a Silverlight project to the solution, which turned on the Silverlight Debugger. This was my problem.
On the property page for the web application -> Start Options -> at the bottom of the page be sure that "Silverlight" is unchecked. Actually, I have only ASP.NET checked and now the debugger goes through Visual Studio.
Unchecking it and now the debugger stops on the "initialize" function as I wanted.

The solution for me was to update the IE from version 9 to 11. Hope it helps to someone. Peace!

You have to wait for the IDE to parse the JavaScript code. Just wait a while and you should see the JavaScript code change color. You will then be able to add breakpoints.

I had the same annoying issues on Visual Studio 2013, and JavaScript development without a debugger is just suicide.
All I did to fix it was to right click the break point red dot -> Disable Breakpoint and then right click again -> Enable Breakpoint.
This made the debugger work on JavaScript like a charm again.

This can also happen when your solution has multiple web projects, even if they're being served from a different ASP.NET Development Server (WebDev.WebServer40.exe) instance on different ports.

If running two or more web projects within your solution and you have multiple script files with the same name at the same place in different webs, the development web-servers may serve up the wrong file, causing this problem.
In my case, deleting the extra copies resolved the problem.

I sometimes have this problem with external JavaScript files - it is caused by the browser cache holding onto an old copy of the file. Forcing a refresh of the page linking to the JavaScript code solves the issue in this case.
Of course, make sure your debugger is attached to the correct browser process. ;)

This is perhaps glaringly obvious, but I stumbled over this for a second, so perhaps others will too. I didn't have Internet Explorer set up to handle HTML/HTTP, and hence it was not launched when I pressed the run button in Visual Studio.
Instead, I was starting Firefox. I went to Start Button | Default Programs, set all the defaults for Internet Explorer, and then debugging started working in Visual Studio for me without any other fuss.