Node.JS - FoalTS framework - Configuration & environment variables

March 8th 2021

@loicpoullainLoïc Poullain

Fullstack developper. Creator of FoalTS.

This article presents some improvements introduced in version 2 of FoalTS:

• Configuration and type safety
• Configuration and

  .env

  files (

  .env

  ,

  .env.test

  , etc)
• Available configuration file formats (JSON, YAML and JS)

Configuration and Type Safety

Starting from version 2, great attention is paid to type safety in the configuration. The

Config.get

const timeout = Config.get('custom.timeout', 'number');
// The TypeScript type returned by `get` is number|undefined.

In this example, when calling the

get

• If the value is not defined, the function returns

  undefined

  .
• If the value is a number, the function returns it.
• If the value is a string that can be converted to a number (ex:

  "1"

  ), the function converts and returns it.
• If the value is not a number and cannot be converted, then the function throws a

  ConfigTypeError

  with the details. Note that the config value is not logged to avoid leaking sensitive information.

If you wish to make the config parameter mandatory, you can do it by using the

getOrThrow

ConfigNotFound

const timeout = Config.getOrThrow('custom.timeout', 'number');
// The TypeScript type returned by `get` is number.

Supported types are

string

number

boolean

boolean|string

number|string

any

Multiple

.env

files support

Version 2 allows you to use different

.env

If your configuration is as follows and

NODE_ENV

production

.env.production

.env

Example of configuration file (YAML)

settings:
  jwt:
    secret: env(JWT_SECRET)

Three config formats (JS, JSON, YAML)

JSON and YAML were already supported in version 1. Starting from version 2, JS is also allowed.

YAML example

settings:
  session:
    store: "@foal/typeorm"

JSON example

{
  "settings": {
    "session": {
      "store": "@foal/typeorm"
    }
  }
}

JS example

module.exports = {
  settings: {
    session: {
      store: "@foal/typeorm"
    }
  }
}

More Liberty in Naming Environment Variables

In version 1, the names of the environment variables were depending on the names of the configuration keys. For example, when using

Config.get('settings.mongodbUri')

SETTINGS_MONGODB_URI

Starting from version 2, it is your responsibility to choose the environment variable that you want to use (if you use one). This gives more flexibility especially when a Cloud provider defines its own variable names.

YAML example

settings:
  mongodbUri: env(MONGODB_URI)

Previously published at https://foalts.org/blog/2021/03/02/whats-new-in-version-2-part-2