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?

Answer 1

(For Node 8 and later)

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

1. 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)

2. 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:

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

Answer 2

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.

Answer 3

To Debug a Node js application, one can use the debug inbuilt module

Insert debugger; statement where you want to insert breakpoints

Run the file with command node inspect index.js

Press C to continue to next breakpoint

you can even debug values associated to variables at that breakpoint by typing repl

For more information, Please Refer https://nodejs.org/api/debugger.html

Answer 4

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!

Answer 5

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.