Overview

Have your configuration in one place, organized in a js native structure, possbily hirarchial, but still easily configurable and overideable by environment variables, as recommended by the Twelve-Factor App methodology

Your config objects can look like below, and still fully support environment variables:

{
  port: 1234,                     // PORT=1234
  isCors: true                    // IS_CORS=true
  db: {
    hostName: 'example.com',      // DB__HOST_NAME=example.com
    port: 4321,                   // DB__PORT=4321
  },
  friends: ['Adam', 'Rachel'],    // FRIENDS__0=Adam FRIENDS__1=Rachel
}

This tiny and powerfull config library reads keys from the config object and searches proccess.env for corresponding keys according to a naming convension.

It allows your apps to use config objects that fully support literal objects, literal arrays, numbers, strings and booleans , while stil being configured/overidden by env vars.

Sample

config.js

const {mapEnv} = require('@welldone-software/env-config')

module.exports = mapEnv({
  port: 1234,
  db: {
    hostName: 'example.com',
    port: 4321,
    user: '',
    password: '',
  },
  friends: ['Adam', 'Rachel'],
  isCors: true
})

Environment variables (specified in .env file or at runtime)

DB__HOST_NAME=mydomain.com
DB__PORT=3060
DB__USER=ADMIN
DB__PASSWORD=ygIYDG*&h8&ADSGH
IS_CORS=false
ANOTHER_KEY=anothervalue
FRIENDS__1=Sara

At runtime, the result will be

{
  port: 1234,
  db: {
    hostName: 'mydomain.com',
    port: 3060,
    user: 'ADMIN',
    password: 'ygIYDG*&h8&ADSGH',
  },
  friends: ['Adam', 'Sara'],
  isCors: false
}

Installing

yarn add @welldone-software/env-config
# or the npm version:
npm i @welldone-software/env-config

Importing

import {mergeEnv, mapEnv, getEnvKeys, getDotEnvFileFormat} from '@welldone-software/env-config';
// or the node version:
const {mergeEnv, mapEnv, getEnvKeys, getDotEnvFileFormat} = require('@welldone-software/env-config');

API

mergeEnv(config: Object) : Object

Recrusively applies values from the environment (environment variables) onto the fileds of the config object parameter and returns the same object, after it has been changed. Note: this changes the object itself, and breaches immutablity thus we recommend using mapEnv.

mapEnv(config: Object) : Object

A pure function version of mergeEnv. This keeps the config object parameter immutable. It creates and returns a new object which is a combination of the original config object values and the values applied from the environment.

getEnvKeys(config: Object) : string[]

A utility function that returns the list of environment keys expected/supported for a given config object.

getDotEnvFileFormat(config: Object) : string

A utility function that returns the dot env file (keys and values) for a given config object.

Conventions

JS

• The JS config object should be a literal object with camalCase members.
• Object can be nested, aka have members which are objects themselves.
• Object fields can be of of either _Object, String, Boolean, Number or Array type.

ENV

• Environment variables are expected in UPPER_SNAKE_CASE convention.
• A single underscore (_) singinfied a word change and is mapped to case changes in js's camalCase.
• Two underscores (__) mean nesting, e.g. DB_SETTINGS__CONNECTION_STRING translated to dbSettings.connectionString
• Boolean values are true and false
• Arrays values are modeled like sub objects, e.g. VAR_NAME__0. Note the double underscore.

Type resolution

Types are determined by defaults in the config object, so you should have a defalut value on each field of the config object. The type of the value will determine the type and shape expected of the corresponding evironment variable.

Advantages

• Single source of truth - one place to define all posibble config keys.
• Simple to use but still allows for rather complex configurations: not just strings and not just flat structures.
• Uses 'native' naming convention in each environment so configs look natural both in JS and in ENV.
• Much more readable than the alternative: const port = proccess.env.PORT || 1000

Roadmap

• Add typing support (typescript and Flow)
• Support initial prefix (only merge prefixed env vars, with and without omitting the prefix)

License

MIT License