config-twelve

Node.js configuration with env variables that adheres to the twelve-factor methodology.

The third factor states config should be stored in the environment. This library makes that processor easier. You define the variables you want to use in a config file. Supports defaults and casts to various types.

This improves over the popular [dotenv])(https://www.npmjs.com/package/dotenv) by

• Allowing the use of types (think TypeScript for env vars)
• Ability to set default values
• Requirement to define what environment variables your application will use
• Providing an easy interface
• One location for new developers to see all config needed

Setup

Install with NPM

npm i config-twelve

Add a file named config.js to the root folder of your application (same place package.json is located). Here is an example to get started.

module.exports = {
  DATABASE_URI: 'string',
  DATABASE_MAX_CONNECTIONS: 'number',
  REPORTS_EMAIL: {
    default: '[e-mail]'
  },
  DEBUG_OUTPUT: {
    type: 'boolean',
    default: false
  }
}

In the example DATABASE_URI and DATABASE_MAX_CONNECTIONS are both required environment variables. You can set these before running your application with:

export DATABASE_URI="sqlite:/tmp/database.db"
export DATABASE_MAX_CONNECTIONS=100

Now you are ready to use the config in your app:

const config = require('config-twelve')
 
console.log(config.DATABASE_URI) // sqlite:/tmp/database.db
console.log(config.DEBUG_OUTPUT) // false

Config file

The config.js file sets up what variables you want to use for configuration.

Type

Each configured variable has a type. The default is a string, and unknown types are treated as strings.

number is cast to a number

boolean handles the falsey values of: false, f, n, no, off, 0, (emtpy string). Everything else is true.

You can declare the type using a string:

module.exports = {
  ENV_VAR_NAME: 'boolean'
}

Or as an option:

module.exports = {
  ENV_VAR_NAME: {
    type: 'boolean'
  }
}

Required

By default all environment variables are required. If a required variable is missing in the environment, an exception will be thrown. If the variable has a default value it is not required. You can also set the required option to false:

module.exports = {
  ENV_VAR_NAME: {
    required: false
  }
}

Default

If the default option is set, the value is used if the variable is missing in the environment.

module.exports = {
  ENV_VAR_NAME: {
    default: 'foobar'
  }
}

For more examples of the config file, see the config used for the integration tests.

Usage

Every variable becomes a property on the config object:

const config = require('config-twelve')
 
console.log(config.ENV_VAR_NAME)

Contributing

After pulling the repository setup with npm install

Running tests: npm test

Check style: npm run lint