Passing environment variables in npm-scripts

Question

I have a package.json with following (simplified) content in the scripts key:

...
scripts: {
   "start": "NODE_ENV=${NODE_ENV:=production} node start-app.js",
   "poststart": "echo $NODE_ENV"
}
...

From the command line I can run:

npm start

This will run my start-app.js script and set the process.env.NODE_ENV environment variable to "production". See here for syntax explanation.

The poststart will automatically run after start as described here .

However poststart will not "inherit" the NODE_ENV shell environment variable, so the echo command will not echo anything.

My producation code is a little more complex, but what I am trying to accomplish is passing down the NODE_ENV variable from the "starting point" to dependent scripts. Any suggestions/best practices on how to do that?

I dont want to hardcode the NODE_ENV in the poststart, because I might want to do:

NODE_ENV=development npm start

and I want everyting "down the chain" inherit the same environment.

Answer 1

You have a few options:

• better-npm-run ,which can define an env for each command separately
• Instead of a poststart script, you can concatenate commands for npm like so: "start": "NODE_ENV=${NODE_ENV:=production} node start-app.js && echo $NODE_ENV"
• Use a process manager in production like pm2 . pm2 lets you define environment specific json files with settings such as NODE_ENV . At our company, we successfully run all of our apps in different environments with pm2 (all the while having the same start command)

Answer 2

this is how I did it, first you need to install two dev-dependencies

https://www.npmjs.com/package/env-cmd this load your env var from your file

https://www.npmjs.com/package/cross-env this use environment variable in script

example scripts:

"env-cmd ./.config/prod.env cross-env-shell \"docker volume create $DOCKER_VOLUME\""

this load $DOCKER_VOLUME env var from prod.env

update: starting from env-cmd version 10, you need specify -f flag if you want to use a custom env file path

"env-cmd -f ./.config/prod.env cross-env-shell \"docker volume create $DOCKER_VOLUME\""

Answer 3

If you have small use cased, use better-npm-run. For small cases, it works fine. Somehow if you have a lot of commands and it hard manage. Try, batman-cli . Work well and handle lot of environment-dependent issues

npm i -g batman-cli