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Newbie question here, it seems... I'm losing my mind. Why is this so hard? I've been programming other languages for years, but I'm relatively new to node and JS. I've read and watched as much as I can find official and unofficial on the web about this and it's either years old or significantly different from my situation, so not very helpful.
I'd really, really appreciate anyone who can understand my (pretty simple, I would have thought!?) specific case and help me get this set up to just work. Possible?
macOS 10.15.6 Catalina.
As I understand it, node comes with the OS. It's Node.js 12.8.1
VS Code 1.48.2
I create a new file, name it abcd.js. VS Code figures out it's javascript. I add some code - read a file of JSON from the disk, make some changes, console.log some stuff (appears under the Output tab). I run it.* All good and works.
Now... Run menu > "Start Debugging". Or, There's a Run/Debug icon in the sidebar that shows a "Run and Debug" button which I click on. Both of those ask me for an environment - I choose Node.js, and the Debug console outputs this:
/usr/local/bin/node path/to/my/file.js
Debugger listening on ws://127.0.0.1:56430/30b0c2aa-278b-4540-94c4-825d30b94f57
For help see https://nodejs.org/en/docs/inspector
And that's it. I have breakpoints, but it doesn't stop on them. Something happens (too quick to see what it is). I don't think it's actually running my code because nothing new shows up under the Output tab.
There's also a note in that sidebar saying "To customize Run and Debug create a launch.json file." I've experimented with that as much as I can, but nothing I do seems to help.
I've been programming for years. I'm used to other languages and IDEs (eg. C, Java, AppleScript, Swift, others), where you open the IDE, write some code, hit run (or debug), it may or may not build a target (depending on the language and environment), but then it runs the code (opens the target app, or runs in the IDE, and allows you to step through the code, breakpoints, etc. in the IDE if debugging). Is JS/node programming radically different from this somehow?
*One theory:
I'm not doing this through any terminal or any browser. Maybe that's the problem...? At some point I installed a "Code Runner" plugin that I believe is what is running my code. It was a while ago, but if I recall correctly maybe I turned to that because I was looking for the experience I've described above, and this plugin gave me that where the "normal" node setup process didn't? Perhaps my problem is that that plugin simplifies RUNNING js scripts so much that my issues with DEBUGGING exist because that plugin allows me to bypass other usual complications with running JS/Node scripts (but doesn't have any debugging functionality of its own)?
My thanks to #ippi for his/her comment with a gif video. Not sure if the following really answers my question, but I'm posting it in case it helps anyone else.
I took some time to clean up my Mac a little, and I completely uninstall VSCode, all its extensions and supporting files and started again.
I re-installed Code from scratch, didn't add any extensions, and then tried what #ippi's video showed.
It still didn't work - I got more or less the same output as in my post, and I'm not sure if it was running the code or not.
I had an urgent deadline to meet so didn't come back to it till now - two days later - and now, it's working.
A couple of things changed in that time though I really don't know what fixed this, if it was either of those or anything else. The two changes I can remember that I've done the last two days are:
Despite my post saying my node was 12.8.1, sometime in the last couple of days it turned into 8.something. I updated it to the latest v12.8.3, and
to meet that deadline I used node inspect myfile.js in Terminal for a bit.
The inspect (mostly) worked to meet my deadline, but still a hassle compared to what's shown in #ippi's video. I definitely wanted to get it working that way.
So… updating node fixed it? Running it in the terminal for a bit fixed it? Something else? I'm at a loss to know what did it. But it's working now.
Thanks again to #ippi for that. It pointed me in a good direction at least - to clean up my install a bit, if nothing else.
Maybe this will help someone else sometime in the future.
It seems the ultimate answer is:
It should just work out of the box (possibly subject to updating node to its latest). If it doesn't then:
The issue most likely isn't that you have to do any fancy configuring or whatnot to make it work.
Instead, most likely something is wrong with your installation and/or OS and you should explore that.
#ippi's video attached in case his/her link ever breaks:
I have a single process node.js application, which I wish to debug with Intellij IDEA 11 32 bits (node.js is 32 bits too).
So, I place an initial breakpoint and run. The debugger stops at the breakpoint, but then it refuses to do any of the following:
step into
go to another breakpoint
pause execution
When I step into, it seems just to run, without stepping through the code. Once running, it ignores any subsequent breakpoints and does not break when I press the pause button.
This issue drives me crazy.
Any ideas on how should I troubleshoot it?
EDIT
More info. After IDEA breaks on the first breakpoint (the only successful time) I try to inspect the variables and am unable to see any. IDEA is stuck on "Collecting data..." The watch window does not work too.
EDIT2
Justed posted an issue to their bug tracking system - http://youtrack.jetbrains.com/issue/IDEA-112925
I've been noticing that IntelliJ's node.js debugger kinda sucks. It's death by 1000 cuts. I love IntelliJ to death, its such a nice IDE. But for node, the debugger has a million different scenarios where breakpoints don't work properly, and another million where it doesn't properly give you access to the in-scope variable values, and another million where it doesn't step properly...
I'm gonna hafta try looking for another tool..
UPDATE 2014-01-13: I've been using IntelliJ's debugger for a while now (having found no other good tool). It seems some of the problems with it are problems with node or v8 itself. Most of the problems I was having have either actually been solved by newer versions of IntelliJ, or by using this workaround:
1. create a file called proxyDebug.js
2. put the following content in it:
require('path/to/the/script/you/want/to/debug.js')
3. point your debugger to that file
Apparently the node.js debugging hooks go buggy at the entrypoint script, so by creating this proxy entrypoint that we don't care at all about, there won't be any weird bugs caused by that in the scripts you do care about. The bugs this workaround fixed were missed breakpoints, predefined variables (exports, module, process, etc) being inaccessible by the debugger, and one or two other things I can't remember.
Last WebStorm version I tried (7.0.3) actually takes ages in collecting data but eventually works. If it seems stuck to you, try to leave it for a minute
This question already has answers here:
"Just My Code" in Chrome JavaScript debugger
(2 answers)
Closed 7 years ago.
Silly question but I'm only finding answers online for other browsers. I'm debugging code but it keeps stopping at breakpoints in jquery code and other third party includes.
Is there anyway to debug only my own code?
Thanks in advance
There is no breakpoint in jQuery code itself but exceptions can happen and your developer tools can stop at exceptions.
To avoid "break on exceptions" you can set the pausing to "Don't stop at exception".
Just click on this icon and switch it to gray.
It will not stop on exceptions then.
Learn more about this here
Internet Explorer now has this feature. I think it's a real shame Chrome hasn't introduced this feature yet. It seems like an easy, no brainer to me. If I have a null object somewhere by mistake I want to see instantly which line of code it's on, but Chrome stops in every caught or uncaught exception in library code which is really annoying.
http://blogs.msdn.com/b/ie/archive/2014/04/14/what-s-new-in-f12-with-windows-8-1-update.aspx
It's called 'just my code' and you can mark jquery for instance as being a library and not something you want to see errors in.
If you are developing Web sites and apps, then you are likely using
3rd party libraries like jQuery or Angular, and typically these
libraries are often minified. We often see developers who are
debugging their code step into library code, and get buried in the
depths of that library, before being able to get back to their code to
debug their issue.
Visual Studio has supported a feature called “Just My Code” (JMC)
managed languages for a while and with Visual Studio 2012, it is also
enabled for JavaScript. The idea behind JMC is that we keep the
debugger in your code, in the code you want to debug and not into code
you can’t really change.
With this feature now in F12, there are two key things you will see
when you debug
You will never ‘step into’ a file (library) that is marked as library
code. You can mark a library through the file picker in the debugger
(see below), even if you have stepped into the file. Once marked, any
step operation will take you to your code.
If you enable “break on all
exceptions” you will never break on an exception thrown and handled in
library code.
I'm very experienced in C/C++/Objective-C and over the last few days have been trying my hand at html/css/JS and am finding it very frustrating.
Time and time and time again I've been caught out as I've a syntax error or undeclared variable due to copying / pasting etc. with the consequence being that the code suddenly stops working then I have to scratch my head and figure out why.
The most painful thing is resorting to sprinkling alerts in the code everything something fails in order to track down the reason. I know there is the new console object for logging but it doesn't seem to work with Komodoedit or jsFiddle? Which is what I've been using.
Is there a way of using these tool, or alternative tools where I can step through the code line by line in a debugger like I can with other languages? Or any tricks for easy detection of problems with the code before executing it in addition to jslint?
[I don't want to use any libraries that might have built-in support for logging etc. as I'm finding they (well JQuery/JQuery mobile is) are drastically slowing down loading times on an iPhone so want to concentrate on pure JS.]
[My target browser is just iOS, but am using Komodoedit with Chrome most of the time and every few hours try it on an iPhone]
Thanks
You need several tools.
First, get yourself a real debugger. I use the one built into Chrome. There's a similar one built into Safari and Firebug available as an add-on for Firefox. This will allow you to set breakpoints and step through your code and see exactly what is happening.
Second, get very used to running your code through jsLint. This will show you many obvious typos and encourage you to write robust code from day one.
Third, start writing in strict mode. This will again prevent some obvious typos and force you to start some good habits.
Fourth, use console.log() when needed. Once you have a debugger, it's output will show in the debug console of the debugger for any page in your browser, including jsFiddle pages. You will have to invoke the debugger on the right frame in jsFiddle and then it will work fine. I use both a regular debugger and console.log() all the time with jsFiddle. It takes a little figuring in jsFiddle and the debugger to find where your own code is to set breakpoints, but once you find it, it's easy to use.
Fifth, javascript is simply not C++. While the syntax will seem quite familiar, the way you do things with anonymous functions and closures and objects and prototypes is very different. As one who programmed in C++ for many, many years before learning javascript, I very much appreciate what I can do now in javascript that was a lot more work in C++, but it took awhile to get my brain into a new mode of thinking. I spent too much time in my first years of javascript development trying to emulate C++ techniques rather than just learning the better way to accomplish the goal in javascript.
Sixth, you will have to change how you write and test code because of the lack of a compiler that finds errors for you. I remember in the days of C++, when I needed to refactor something, I could make a bunch of changes and then let the compiler find all the other places I need to fix the syntax. You can't do that with javascript. When you make mass changes, you can run through jsLint to find some issues and then you literally need to execute every path to make sure everything works. It is a bit of a pain.
Seventh, find a strategy/tools for unit testing. Once a project gets more than a few functions long, you will benefit greatly from building unit tests that you can run anytime you make significant changes. They will both find issues for you in a lot less time than without the unit tests and they will give you the courage to refactor and clean up your code when you see the need for that because you know the unit tests will tell you if everything is working again. It's extra work up front that pays dividends many times over down the road.
Firefox has an add-on called FireBug that is very helpful for debugging CSS/javascript, and yes, it does have the ability to step through a script as well as a command line where you can try out various javascript expressions. I'm pretty sure Chrome has a similar feature.
Here is the article in which you get a list of tools to debug the javascript
advance-javascript-debugging-techniques
Since you're using Chrome, you just need to open the developer console (spanner -> tools -> javascript console, or Ctrl+Alt+J (at a guess)). Instead of sprinkling your code with alerts, use console.log, console.error, and console.info to print to it. All of those are variadic, so you can pass as much to one call as you need.
In addition to this, you can use the console to test and modify parts of your code on the fly, or to just try out a few snippets to see if they work. It's a fully functional REPL that also works with the current document.
In the sources tab of the developer console, you are able to set breakpoints and step through your code, analysing state at each point. This page goes into some detail about it: http://chromedevtools.googlecode.com/svn-history/r421/trunk/tutorials/breapoints/index.html
In the elements tab, you are able to set breakpoints on changes to elements in the DOM, including changes to attributes and child nodes. Right click a node and select the option you want. This will come in handy when debugging code that is asynchronous and plays with the document (eg. AJAX calls inserting new content).
In addition to this, you can scroll to the bottom of the styles pane to the right, and open the event listeners section. Here, you can inspect all the events bound to the selected DOM node.
You can enter debugger (without a semicolon) into your code, and it will open the sources tab at that point so you can inspect the code further. I think this may be Chrome specific.
Finally, tools like JSlint will help you spot undeclared variables as you code, as well as cases where the formatting of your code creates unexpected errors, and some might even go as far as using syntax highlighting to make you notice variables that are undefined.
This is also just scraping the surface. Your editor and JSlint can make your code look right and parse without error, but the browser and its console is where you will spend most of your time.
I have a .js file that normally gets executed by cscript.exe (i.e. is not run in the browser and cannot be run there).
I know, that I can feed cscript.exe the //X parameter in order to get asked for a debugger to choose. Ok. That's fine.
I select "Visual Studio 2005 Debugger", IDE comes up, execution stops on the first line. Fine.
Script terminates (or I terminate it), I edit something and want to debug it again.
Simple thought would be just to hit F5 and run the debugger again. But this doesn't work. VS just tells me that it couldn't find any debugging symbols in cscript.exe:
What now? Starting cscript.exe from the command line again for each debug run is quite cumbersome in my opinion.
Is there a way to simply debug the script with VS? Also hints for other debugging tools would be appreciated.
Edit:
The answer of t0nyh0 is pretty close. I create a dummy console application, compile and the debugger comes up. However, two things are not perfect
cscript.exe always asks for the debugger to use (which instance of VS).
Could this be overcome by specifying a certain debugger instance directly in the command line?
In order to fire a post-build event, there have to be some modifications in the sources. Currently, I simply add/delete a blank line to trigger building of my dummy project.
Is there a way to always execute the post-build script, even if nothing has changed?
There might not be a way to attach the debugger to cscript.exe itself, but you may be able to create a post-build event that runs a batch file that executes the cscript.exe //x myScript.js command so that every time you build, it executes for you automatically.
See this for more information on post-build events: http://msdn.microsoft.com/en-us/library/ke5z92ks(v=vs.80).aspx
While not a debugger tool, you should consider using a JavaScript testing framework for Visual Studio, such as Chutzpah, which will most likely make your life a lot easier.
Along with standard browser debugging tools (Firebug or Chrome Inspector), I've found that's all I usually need to build clean, tested, mostly-bug-free JavaScript code.
I don't have cscript at hand, but I think you can try to attach VS to the process manually.
After you start up your js using cscript.exe //x myScript.js, click "Debug - Attach to Process", find your cscript.exe process and attach to it.
I forget if VS2005 has this function but VS2008 and VS2010 do.
It is the native debug action that VS takes to debug (attach to the running process). If this doesn't work, I don't think you can do this using Visual Studio.
Best Javascript Debugger is Rhino Debugger See http://www.mozilla.org/rhino/debugger.html .
it is open source and you can get the source code of the Debugger GUI.
you can customise it as you wish :-) .