How to debug node js app with breakpoints and everything?

Question

I've installed node-inspector just to find out that it doesn't support breakpoints :| What's the point in it at all, bearing in mind that on big part node code is asynchronous and you simply cannot follow it step by step?..

I'm definitely missing a point here...

Anyway to debug node code with breakpoints and everything?

Possible duplicate: http://stackoverflow.com/questions/1911015/how-to-debug-node-js-applications — beny23, Jul 23 '12 at 11:02
I came here from there - breakpoints do not work in node-inspector and there is no answer to my question. Is there? — jayarjo, Jul 23 '12 at 11:15
It does support breakpoints. I just doesn't 'remember' them when you referesh the inspector page. — JP Richardson, Jul 23 '12 at 14:45
Possible duplicate of [How do I debug Node.js applications?](https://stackoverflow.com/questions/1911015/how-do-i-debug-node-js-applications) — Ciro Santilli OurBigBook.com, Aug 04 '19 at 14:01
Debugging node.js applications has become much better these days. So this question and answers are probably not even actual anymore. — jayarjo, Aug 04 '19 at 16:25

score 26 · Answer 1 · edited Jan 22 '20 at 09:00

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yupp, I've successfully used node-inspector. If you want permanent breakpoints, simply insert debugger; in your code. See http://nodejs.org/api/debugger.html.

Making node wait until a debugger is attached, using node --inspect-brk script.js (previously node --debug-brk script.js), can also be very helpful.

edited Jan 22 '20 at 09:00

Ciro Santilli OurBigBook.com

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answered Jul 23 '12 at 12:29

rdrey

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with debugger; it crashes: node(31848,0x7fff70e12cc0) malloc: *** error for object 0x10010f690: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug Abort trap – jayarjo Jul 23 '12 at 15:31
I've never seen that error, sorry. Is your app's process crashing, or is it node-inspector? Which versions are you running? Are you using any native node modules that could be crashing? – rdrey Jul 24 '12 at 07:14
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For later versions of Node.js, `--debug-brk` is deprecated. Use `--inspect-brk` instead. – Matt Feb 15 '19 at 21:24

Yuci · Accepted Answer · 2019-01-15T16:52:20.313

(For Node 8 and later)

Node.js has a built-in debugger. Normally you can turn on the debugger in two ways:

Start your Node.js app or script with the --inspect or --inspect-brk switch. For example:

$ node.js --inspect index.js

(Note: --inspect-brk breaks before user code starts)

If for some reason you cannot start your Node.js app or script with the --inspect switch, you can still instruct the Node.js process to start listening for debugging messages by signalling it with SIGUSR1 (on Linux and OS X). For Node 8 and later it will activate the Inspector API, same as the --inspect switch

$ kill -sigusr1 23485

(Note: you need to replace 23485 with your own Node.js process ID)

With the debugger turned on, you can open the Google Chrome browser, and type in the address bar chrome://inspect

Then you should see an entry listed under "Remote Target". Go ahead and click "inspect".

Now you can set breakpoints and start debugging your code.

Reference:

https://nodejs.org/en/docs/guides/debugging-getting-started/
Related issue on stackoverflow: Chrome Devtools Dedicated Node.js Inspector not stopping at breakpoints

To do everything in the terminal, you need `node inspect` instead as explained at: https://stackoverflow.com/a/55429798/895245 as of `v10.15.1`. — Ciro Santilli OurBigBook.com, Jan 22 '20 at 09:05
I've made a video which shows the inspect setup with Node.js (and TypeScript if needed): https://www.youtube.com/watch?v=bV-DHjmwuZ0 — Benny Code, Mar 23 '21 at 14:15

score 9 · Answer 3 · edited Dec 19 '21 at 15:16

9

To debug a Node.js application, one can use the debugging built-in method:

(1) Insert debugger; statement where you want to insert a break point
(2) Run the file with command $ node inspect <file name>
(3) Use a key for example, c to continue to next break point

You can even debug values associated to variables at that break point by typing repl. For more information, Please check the official guide.

edited Dec 19 '21 at 15:16

Cloud Cho

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answered Mar 30 '19 at 09:01

Shekar Mania

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Tested on `v10.15.1`. – Ciro Santilli OurBigBook.com Jan 22 '20 at 09:04
If you don't want to modify your code, you can use the function `setBreakpoint` or `sb` to set up a breakpoint, eg `setBreakpoint('script.js', 1)` (https://nodejs.org/api/debugger.html) – Jean Paul Oct 05 '20 at 15:42

Alvaro · Answer 4 · 2019-06-10T13:30:23.493

Have you tried using nodemon library? it can be found here.

For development purposes you could start the app running nodemon. I have this script:

"dev": "nodemon --inspect src/index.js"

It will break any time a debugger statement is reached in the code. To open the console where you can see the server code, open the console in chrome and click on the nodejs icon:

It also helps you refreshing the server every time you save any file on the server.

Let me know if it works!

score 1 · Answer 5 · answered Apr 29 '14 at 17:32

1

Just to elaborate a bit here:

Set a debugger wherever you want the breakpoints to be and then run your code with node debug script.js/index.js

When the debugger stops at you breakpoint, you will need to repl to inspect the variables.

answered Apr 29 '14 at 17:32

bsiddiqui

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i want a breakpoint wherever an exception happens (let's say I don't know ahead of time where that will be). how do i do that? – Michael Jul 01 '17 at 03:35
you can instead of using REPL command add runtime watchers, just type for ex. `watch('count') ` watchers api will print the value when debugger stops in that function. – Tarandeep Singh Oct 19 '17 at 10:04

How to debug node js app with breakpoints and everything?

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