How to detect dev vs production

Forgive me if this is an extremely basic question, but I’m struggling to figure out how to determine if my code is running in dev or production.

I tried adding env vars to my scripts in package.json:

  "scripts": {
    "dev": "ENV=dev next",
    "build": "ENV=production next build",
    "start": "ENV=production next start"
  }

though I don’t know how to access these variables. I tried:

const ENV = 'undefined' !== typeof window ? window.ENV : process.ENV

but this didn’t seem to work. These variables don’t show up in window object from browser.

From my understanding, window is available on client and process is available on server, but I’m not sure how to set a var on them, or access that var appropriately. Alternatively, is there an existing variable that indicates production vs dev mode?

Thanks!

[sedubois]

I suggest to use NODE_ENV.

[malixsys]

In case someone (else) comes here through Google, check this example…