1.4.0 • Public • Published

Node.js Custom Environment Variables Generator for config-Based Projects

This is a handy little utility that will generate JSON suitable for use as a config -based project's config/custom-environment-variables.json. (Note that throughout this project "cev" stands for "custom environment variables".)

NOTE: This package supercedes https://www.npmjs.com/package/config-cev-generator

See this blog post for full description and tips.

It really comes in handy when your configuration starts to get big and you forget to keep your config/custom-environment-variables.json file in sync with the rest of your configuration.

NOTE: If you're using TypeScript, make sure ts-node is on your PATH and that you use cev-ts instead of cev.


# cd into a config-based Node.js project...
$ npm install --save-dev @northscaler/config-custom-environment-variables-generator
$ npx cev

If your project's configuration is

  "foo": {
    "bar": "snafu",
    "goo": "juju"

then the preceding command will generate JSON to stdout suitable for use as your project's config/custom-environment-variables.json:

  "foo": {
    "bar": "NODE_APP_FOO_BAR",
    "goo": "NODE_APP_FOO_GOO"

In order to support config's __format feature, see the following example. If your project's configuration is

  "foo": {
    "bar": 1,
    "goo": 2
  "snafu": "something"

then the following command will cause your configuration's foo.bar value to use format json and foo.goo to use number:

npx cev -k foo.bar=json -k foo.goo=number

The CLI writes to stdout by default. To save the output, just direct it to a file:

$ npx cev > config/custom-environment-variables.json

... or give the file as the sole positional argument:

$ npx cev config/custom-environment-variables.json


The generator requires that your project have a valid config-based configuration in order to work properly.


  • The default environment variable prefix is NODE_APP. Customize with -p or --prefix.
  • The default word separator is _. Customize with -s or --separator.
  • Run cev --help for more information.

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npm i @northscaler/config-custom-environment-variables-generator

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