Develop Reference

Is it possible to avoid breaking on a debugger statement in Chrome?

I'm trying to reverse engineer a heavily obfuscated JS and one of the tricks the author does is to continuously call the debugger statement from within an anonymous function:
Unfortunately, I cannot right click and Never pause it, because each time the function is called a new anonymous function is spawned. The only way for me to inspect the code with DevTools open is to toggle the Disable all breakpoints button, but that disables my breakpoints too.
Is there any way to disable exclusively all debugger statements in Chrome?
In case there isnt, what could be done to bypass this anti-tampering trick?

Download the offending webworker.js file to your local drive, and use a text editor to replace all occurrences of "debugger" with ";".
Then use a Chrome extension to replace the remote resource with your local modified version.
https://chrome.google.com/webstore/detail/resource-override/pkoacgokdfckfpndoffpifphamojphii?hl=en
FYI: I do not endorse the above extension. It was just the first I found via Google.

This answer is for an old Chrome prior to 2021 where we could hack the internals of devtools itself by using devtools-on-devtools:
undock devtools into a separate window
press the full devtools hotkey - CtrlShifti or ⌘⌥i
paste the following code in this new devtools window console and run it
{
const rx = /\bdebugger\b/y;
const eventSymbol = SDK.DebuggerModel.Events.DebuggerPaused;
const original = [...SDK.targetManager._modelListeners.get(eventSymbol)]
.find(v => v.listener.name === '_debuggerPaused');
const debuggerModel = SDK.targetManager.models(SDK.DebuggerModel)[0];
SDK.targetManager.removeModelListener(
SDK.DebuggerModel,
eventSymbol,
original.listener,
original.thisObject);
SDK.targetManager.addModelListener(
SDK.DebuggerModel,
eventSymbol,
async function({data}) {
if (data._debuggerPausedDetails.reason === 'other') {
const frame = data._debuggerPausedDetails.callFrames[0];
const code = await frame._script.requestContent();
let {columnNumber: x, lineNumber: y} = frame._location;
let pos = 0;
while (y--)
pos = code.indexOf('\n', pos) + 1;
rx.lastIndex = Math.max(0, pos + x);
if (rx.test(code)) {
debuggerModel.resume();
return;
}
}
original.listener.apply(original.thisObject, arguments);
});
}
Notes:
You can save this code as a snippet in devtools to run it later.
To quickly switch docking mode in the main devtools press CtrlShiftD or ⌘⇧D
Theoretically, it's not that hard to put this code into resources.pak file in Chrome application directory. There are several tools to decompile/build that file so just add the code to any script that has something like SDK.DebuggerModel.Events.DebuggerPaused inside. One can even write a tool that does that automatically on Chrome update.

Right-click the in the gutter on the line with the debugger statement and select "Never pause here".

Reloading and debugging JavaScript in TVOS simulator

I have started looking at tutorials for making TVML/TVJS based apps for the new Apple TV, and I have two problems that makes the development process very tedious and impractical.
First thing I am having trouble understanding is how I am supposed to debug code that happens on startup of the application. I have connected the Safari debugger, and I do manage to hit some breakpoints, but only for code that is triggered by some user input. On startup I am loading an xml document from a remote location, and I will use this to dynamically generate the tvml template, but I cannot get the debugger to stop anywhere in the code that is running before the template is done rendering.
The other anti-productive problem I have is that I cannot seem to reload the JavaScript files in any other way than completely shutting down the application in the simulator (double-click the home button, and swipe the app away). This also makes the debugger quit, so I have to restart that one as well. This surely cannot be the way you are supposed to do continuous development and testing?

You can make the debugger stop at the first line when you choose the Auto Pause and Auto Show options from the Safari menu "Develop/Simulator".
You are correct about the exit issue.
One thing you can also try is to run App.reload() from the Safari Debugger console.
This also restarts the app, maybe in the future they can make it work so the debugger will not be gone.
But at the moment this also does not solve the issue.

For manual debugger output (aka console.log()), you could redirect the logging to the Xcode debugger.
(somewhere on the web) I found a way to actually do that, in short it looks like...
AppDelegate.Swift
func appController(appController: TVApplicationController, evaluateAppJavaScriptInContext jsContext: JSContext) {
let jsInterface: cJsInterface = cJsInterface();
jsContext.setObject(jsInterface, forKeyedSubscript: "swiftInterface")
}
App.js
// re-route console.log() to XCode debug window
var console = {
log: function() {
var message = '';
for(var i = 0; i < arguments.length; i++) {
message += arguments[i] + ' '
};
swiftInterface.log(message)
}
};
JsInterface.Swift
#objc protocol jsInterfaceProtocol : JSExport {
func log(message: String) -> Void
}
...
class cJsInterface: NSObject, jsInterfaceProtocol {
func log(message: String) -> Void {
print("JS: \(message)")
}
}
Complete sources in github: https://github.com/iBaa/PlexConnectApp/tree/f512dfd9c1cb2fbfed2da43c4e3837435b0b22af
I don't have any solution for the dying debugger myself...

Debug output in tests

How do I output some information in Postman tests?
console.log(tv4.error);
tests["Valid Data1"] = tv4.validate(data1, schema);
console.log() seems to be working but I want to output my info into the same panel where my assertions go (for easier correlation):

Just make a fake test that passes:
var jsonData = JSON.parse(responseBody);
tests["id = " + jsonData.id] = true; // debug message
tests["name = " + jsonData.name] = true; // debug message

Reference for the people who just want to use Chrome’s Developer Tools (which will let you see console output and give you many more features)
To enable it
Type chrome://flags inside your Chrome URL window
Search for "Debugging for packed apps" setting
Enable the setting
Restart Chrome
You can access the Developer Tools window by right clicking anywhere inside Postman and selecting "inspect element".
You can also go to chrome://inspect/#apps and then click "inspect"
Reference

I used this, which isn't the prettiest, but it works for what I needed.
tests["your test name here " + data.data.length] = data.data.length > 100;

Piggybacking on the other answers, just define a function in your Postman test code
var print = function(s){
tests[s] = true;
};
then consume it like
print("current value of x: " + x);

Now You have got sth called "Postman Console" To run it please type CTRL + ALT + C
For mor info see here: https://blog.getpostman.com/2016/08/26/the-postman-console/

One of the way is use the tests[""+value].
e.g
http://api.openweathermap.org/data/2.5/weather?q=London,uk&appid=Your_API_Key.
Response :

Similar to a previous answer regarding an alternate option: using dev tools. However, if you are using the native app, right clicking to get the dev tools won't work.
Instead,
Head to View in the application menu, and click on "Show DevTools".
In the DevTools window, clicking on the top level Console tab should show the app’s debug logs.
Reference: https://learning.getpostman.com/docs/postman/collection_runs/debugging_a_collection_run

javascript. formatting console.log

I´m working on a big angular.js project.
Now, I´ve to profile some pages about the performance.
With the console.log of the project I´m looking for the performance problems.
I miss if console.log can output the current time (yes, I know in Chrome you can set up).
Is there a way (like in log4java) to format the output?
Thanks in advance,

Be careful, the console object should not be activated in production mainly because it can breaks the code for some users (for example IE8 or less users).
But if you want to test on a tool that you know, you can use the Web API interface which provides some useful method on this object:
https://developer.mozilla.org/en-US/docs/Web/API/Console
(This doc is from the Mozilla Developer Network (MDN) and therefore mainly applies to Firefox, but at the end of that page you can find links to the corresponding docs for the IE, Chrome and Safari DevTools as well as Firebug).
For example, you can use the time() method for your use case:
console.time("answer time");
// ... some other code
console.timeEnd("answer time");
Outputs something like this:

You could try something like this:
console = window.console ? console : {};
native_log = console.log;
window.console.log = function myConsole() {
// Cannot log if console.log is not present natively,
// so fail silently (in IE without debugger opened)
if (!native_log)
return;
var args = Array.prototype.slice.call(arguments);
args.unshift(new Date());
native_log.apply(console, args);
}
console.log('hello'); // Date 2014-12-02T14:14:50.138Z "hello"
Of course, you would not let the new Date() as is, but it gives you the idea.

Checking if user has a certain extension installed

I just found out that the Screen Capture by Google extension makes my website's window.onresize event not fire.
I want to perform a javascript check to see if the user has ScreenCapture installed and if so, warn the user of the problem.
A year ago I think I heard of some javascript code that could do this, maybe using some google API, but I don't remember.
Any insight on this? I haven't developed any extensions so I don't really know how they work.
[EDIT]
So I have been asked to show some code. As seen in my previous question ( window.onresize not firing in Chrome but firing in Chrome Incognito ), the problem occurs on any window.onresize event function, so I don't think my code really matters.
Also, there is quite a lot of my code, I don't know how much of it to paste or if it would be helpful.
var debounce = function (func, threshold, execAsap)
{
var timeout;
return function debounced () {//alert("1.1 Y U NO WORK?");
var obj = this, args = arguments;
function delayed () {
if (!execAsap)
func.apply(obj, args);
timeout = null;
}
if (timeout)
clearTimeout(timeout);
else if (execAsap)
func.apply(obj, args);
timeout = setTimeout(delayed, threshold || 100);
};
};
window.onresize = debounce(function (e) { //alert("1.2 Y U NO WORK?");
flag = true;
var point = window.center({width:1,height:1});
doCenter(point);
// does something here, but only once after mouse cursor stops
}, 100, false);
I would like to stress that the problem is not due to the debounce. window.onresize = t; function t (e) { alert("wtf?");} won't work either.
[EDIT2]
Here's the result:
var screenCapture = null;
var screenCaptureImg = document.createElement("img");
screenCaptureImg.setAttribute("src", "chrome-extension://cpngackimfmofbokmjmljamhdncknpmg/images/arrow.png");
/*
* Add event listeners for both "load"- and "error"-event
* Set the variable showing the existence of the extension by
* setting it to "true" or "false" according to the fired event
*/
screenCaptureImg.addEventListener("load", doLoad, false);
function doLoad(e){
screenCapture = true; //removeImgTag(e);
alert("I've so cleverly detected that your Chrome has the ScreenCapture extension enabled. \n\nThis extension interferes with my website's DOM and long story short, it won't be able to scale properly.\n\nSo please disable it. \nConsider this extension: \"Disable All Extensions Plus\", it's a handy selective disabler.");
}
screenCaptureImg.addEventListener("error", function(e){
screenCapture = false; //removeImgTag(e);
}, false);
/*
function removeImgTag(e) {
e.currentTarget.parentNode.removeChild(e.currentTarget);
}
*/
Note that I couldn't get removeImgTag to work, because (at least in chrome), I don't seem to have access to the document object in order to create or remove elements from my page, from within these event functions. This is also why I'm displaying an alert instead of elegantly writing up a document.getElementById("something").innerHTML=...

To detect if an extension is installed in Chrome, you can check for a known resource included in the extension such as an image. Resources for the extension are referenced using the following URL pattern:
chrome-extension://<extensionID>/<pathToFile>
The basic detection technique involves creating a hidden image tag and attaching load and error events to it to see if the image loads (as described here for Firefox):
extensionImg.setAttribute("src", "chrome-extension://<INSERT EXTENSION ID HERE>/images/someImage.png"); // See below for discussion of how to find this
/*
* Add event listeners for both "load"- and "error"-event
* Set the variable showing the existence of the extension by
* setting it to "true" or "false" according to the fired event
*/
extensionImg.addEventListener("load", function(e) {
extensionExists = true;
removeImgTag(e);
}, false);
extensionImg.addEventListener("error", function(e) {
extensionExists = false;
removeImgTag(e);
}, false);
function removeImgTag(e) {
e.currentTarget.parentNode.removeChild(e.currentTarget);
}
Check the installation directory of the extension in the Chrome configuration to find a likely target for detection. On my Linux workstation extensions are located in:
~/.config/chromium/Default/Extensions
You can see that I have 3 extensions installed right now:
~/.config/chromium/Default/Extensions$ ls
cpecbmjeidppdiampimghndkikcmoadk nmpeeekfhbmikbdhlpjbfmnpgcbeggic
cpngackimfmofbokmjmljamhdncknpmg
The odd looking names are the unique IDs given to the extension when it is uploaded to the Chrome webstore. You can obtain the ID either from the webstore or by going to the Extensions tab (wrench -> Extensions) and hovering over the link to the extension in question, or "Screen Capture (by Google)" in this case (note the asterisked extension ID):
https://chrome.google.com/webstore/detail/**cpngackimfmofbokmjmljamhdncknpmg**
In the extension directory there will be one or more versions; you can ignore this. Within the version directory is the actual content of the extension:
~/.config/chromium/Default/Extensions/cpngackimfmofbokmjmljamhdncknpmg/5.0.3_0$ ls
account.js images page.js sina_microblog.js
ajax.js isLoad.js picasa.js site.js
background.html _locales plugin style.css
editor.js manifest.json popup.html ui.js
facebook.js notification.html sha1.js upload_ui.js
hotkey_storage.js oauth.js shortcut.js
hub.html options.html showimage.css
i18n_styles page_context.js showimage.html
In the case of the Screen Capture extension there are a number of images to use:
~/.config/chromium/Default/Extensions/cpngackimfmofbokmjmljamhdncknpmg/5.0.3_0/images$ ls
arrow.png icon_128.png icon_save.png print.png
copy.png icon_16.png line.png region.png
cross.png icon_19.png loading.gif screen.png
custom.png icon_32.png loading_icon.gif sina_icon.png
delete_account_icon.png icon_48.png mark.png toolbar_bg.png
down_arrow.png icon_close.png picasa_icon.png upload.png
facebook_icon.png icon_copy.png popup_bg.jpg whole.png
These can be referenced under this URL:
chrome-extension://cpngackimfmofbokmjmljamhdncknpmg/images/arrow.png
This technique obviously depends on the stability of the content of the extension. I recommend using an image that looks likely to remain through all versions.
As mentioned above, the same technique can be used to detect Firefox extensions. In this case the content URL looks like this:
chrome://<EXTENSION NAME>/content/<PATH TO RESOURCE>
On my Linux workstation Firefox extensions are located in:
~/.mozilla/firefox/<USER PROFILE ID>/extensions
Where <USER PROFILE ID> looks something like this: "h4aqaewq.default"
You can see that I have 2 extensions installed right now, one of which is a directory installation and the other of which is a XPI (pronounced "zippy") file:
~/.mozilla/firefox/h4aqaewq.default/extensions$ ls
{3e9a3920-1b27-11da-8cd6-0800200c9a66} staged
firebug#software.joehewitt.com.xpi
The "staged" directory is where Firefox keeps extensions that will be updated (I think). The GUID directory with the brackets is a directory-based extension installation, and the .xpi file is Firebug.
Note: XPI is going away (see the link above). It's basically a zip file that can be opened and inspected by anything that understands zip. I used Emacs.
Finding the extension ID in Firefox is a bit more involved. Go to "Tools -> Add-ons", click the Extensions tab, click the "More" link next to the extension description, then click the "reviews" link to go to the Firefox extension site and get the ID from the URL (note the asterisked extension ID):
https://addons.mozilla.org/en-US/firefox/addon/**firebug**/reviews/?src=api
There's probably an easier way to do this; suggestions welcome.
TODO: how to find a likely image in a Firefox extension.
As an extra note, in Chrome you can only communicate with an extension via the shared DOM of the page: Host page communication