BolajiOlajide / lazy-config

Lazily evaluate functions in config

Lazy Config

Thanks Dane for helping polish the module.

Our team uses this module to lazily evaluate configuration settings, such as environment variables, for our applications.

Install

$ yarn install lazy-config

Ensure that you have a config/default.js and optionally config/{NODE_ENV}.js file for environment overrides

Usage

Lazily evaluate an environment variable

config/default.js

module.exports = {
  isDev: () => process.env.NODE_ENV === 'development',

  db: {
    userName: 'user',
    password: () => {
      return process.env.DB_PASSWORD
    }
  }
}

index.js

const config = require('lazy-config')

// accessing a specific config setting will evaluate the function
console.log('config.db.password', config.db.password)

$ DB_PASSWORD=supersecure node .

// output
$ config.db.password supersecure

Throw when accessing a required environment variable

config/default.js

module.exports = {
  isDev: () => process.env.NODE_ENV === 'development',

  db: {
    userName: 'user',
    password: () => {
      if(!process.env.DB_PASSWORD) {
        throw new Error('Missing environment variable DB_PASSWORD')
      }

      return process.env.DB_PASSWORD
    }
  }
}

index.js

const config = require('lazy-config')

// accessing a specific config setting will evaluate the function
console.log('config.db.password', config.db.password)

// don't set an environment variable
$ node .

// output
$ throws an error complaining about missing DB_PASSWORD