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)