How to enable debugging express.js/node.js application

Question

I am working on express.js in window environment. I have successfully started my project with npm start. Now I need to add debug statement in package.json file to enable debugging.

Like this:

"scripts": {
  "start": "DEBUG=fibonacci:* node ./bin/www"
}

After I have edited in package.json and npm start command I am facing error:

Error: Debug is not an internal or external command

Note: I am following Node.js book and in the book it executes successfully.

jbandi · Accepted Answer · 2017-09-29 08:56:00Z

5

Setting environment variables in npm scripts is platform specific.

On Windows:

"start": "set DEBUG=fibonacci:*&& mocha --reporter spec"

On Unix / macOS:

"start": "DEBUG=fibonacci:* mocha --reporter spec"

I recommend to use cross-env (npm i -D cross-env), which deals with those differences and works on all platforms:

"start": "cross-env DEBUG=fibonacci:* mocha --reporter spec"

answered Sep 29, 2017 at 8:56

jbandi

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Comments

Alessio Campanelli · Accepted Answer · 2017-03-08 13:05:02Z

2

i think you must set DEBUG as a environment variable

set DEBUG=you_application

answered Mar 8, 2017 at 13:05

Alessio Campanelli

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6 Comments

Atul Saini Over a year ago

that way it works...but it temporarily ,i mean closing and starting the command prompt i need to set it again.Is there any way it can work by editing the package.json???

Alessio Campanelli Over a year ago

if you try from console: 1. cd in your app 2. npm install 3. set DEBUG=app 4. npm start It should not be temporary...

David R Over a year ago

But, he will have to repeat these steps, everytime when he opens up a new CMD window right?

Alessio Campanelli Over a year ago

with WebStorm, i set this variable from Edit Configurations... in windows i think it's possible in this way: - Use the global Search Charm to search "Environment Variables" - Click "Edit system environment variables" - Click "Environment Variables" in the dialog. - In the "System Variables" box, search for Path and edit it to include C:\Program Files\nodejs .

Atul Saini Over a year ago

iam not sure how it will help after adding path C:\Program Files\nodejs,but i tried and it not works

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Atul Saini · Accepted Answer · 2017-03-12 17:07:34Z

2

Answers above are correct but they are just cmd session based ,if we close cmd then we need to set the debug variable again. after some debugging i found the correct way

"scripts": {
  "start": "set DEBUG=fibonacci:* & node ./bin/www"
}

we just need to put the set command in the package.json file itself,In that way you can store as many as variable you want like port also.

answered Mar 12, 2017 at 17:07

Atul Saini

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Comments

Modro · Accepted Answer · 2019-08-07 07:59:45Z

1

The way I do it:

set DEBUG=your_project:* & npm start

edited Aug 7, 2019 at 7:59

answered Mar 8, 2017 at 13:27

Modro

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Comments

Mansur Ali Koroglu · Accepted Answer · 2020-06-09 05:45:55Z

0

With nodemon, on windows:

"scripts": {
  "start": "SET \"DEBUG=express:*\"&& nodemon ./bin/www"
},

answered Jun 9, 2020 at 5:45

Mansur Ali Koroglu

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