How to Set Environment Variables from Within Package. Json?

Just use NPM package cross-env. Super easy. Works on Windows, Linux, and all environments. Notice that you don't use && to move to the next task. You just set the env and then start the next task. Credit to @mikekidder for the suggestion in one of the comments here.

From documentation:

{
  "scripts": {
    "build": "cross-env NODE_ENV=production OTHERFLAG=myValue webpack --config build/webpack.config.js"
  }
}

Notice that if you want to set multiple global vars, you just state them in succession, followed by your command to be executed.

Ultimately, the command that is executed (using spawn) is:

webpack --config build/webpack.config.js

The NODE_ENV environment variable will be set by cross-env

I just wanted to add my two cents here for future Node-explorers. On my Ubuntu 14.04 the NODE_ENV=test didn't work, I had to use export NODE_ENV=test after which NODE_ENV=test started working too, weird.

On Windows as have been said you have to use set NODE_ENV=test but for a cross-platform solution the cross-env library didn't seem to do the trick and do you really need a library to do this:

export NODE_ENV=test || set NODE_ENV=test&& yadda yadda

The vertical bars are needed as otherwise Windows would crash on the unrecognized export NODE_ENV command. I don't know about the trailing space, but just to be sure I removed them too.

Because I often find myself working with multiple environment variables, I find it useful to keep them in a separate .env file (make sure to ignore this from your source control). Then (in Linux) prepend export $(cat .env | xargs) && in your script command before starting your app.

Example .env file:

VAR_A=Hello World
VAR_B=format the .env file like this with new vars separated by a line break

Example index.js:

console.log('Test', process.env.VAR_A, process.env.VAR_B);

Example package.json:

{
  ...
  "scripts": {
    "start": "node index.js",

    "env-linux": "export $(cat .env | xargs) && env",
    "start-linux": "export $(cat .env | xargs) && npm start",

    "env-windows": "(for /F \"tokens=*\" %i in (.env) do set %i)",
    "start-windows": "(for /F \"tokens=*\" %i in (.env) do set %i) && npm start",

  }
  ...
}

Unfortunately I can't seem to set the environment variables by calling a script from a script -- like "start-windows": "npm run env-windows && npm start" -- so there is some redundancy in the scripts.

For a test you can see the env variables by running npm run env-linux or npm run env-windows, and test that they make it into your app by running npm run start-linux or npm run start-windows.

Try this on Windows by replacing YOURENV:

  {
    ...
     "scripts": {
       "help": "set NODE_ENV=YOURENV && tagove help",
       "start": "set NODE_ENV=YOURENV && tagove start"
     }
    ...
  }

@luke's answer was almost the one I needed! Thanks.

As the selected answer is very straightforward (and correct), but old, I would like to offer an alternative for importing variables from a .env separate file when running your scripts and fixing some limitations to Luke's answer. Try this:

::: .env file :::

# This way, you CAN use comments in your .env files
NODE_PATH="src/"

# You can also have extra/empty lines in it
SASS_PATH="node_modules:src/styles"

Then, in your package json, you will create a script that will set the variables and run it before the scripts you need them:

::: package.json :::

scripts: {
  "set-env": "export $(cat .env | grep \"^[^#;]\" |xargs)",
  "storybook": "npm run set-env && start-storybook -s public"
}

Some observations:

• The regular expression in the grep'ed cat command will clear the comments and empty lines.

• The && don't need to be "glued" to npm run set-env, as it would be required if you were setting the variables in the same command.

• If you are using yarn, you may see a warning, you can either change it to yarn set-env or use npm run set-env --scripts-prepend-node-path && instead.