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.

Answer 1

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"

Answer 2

i think you must set DEBUG as a environment variable

set DEBUG=you_application