envfefe

This typescript/javascript package parses environment variables – despite the constant negative press envfefe

Disclaimer: the author of this package opposes Trump and other racists and misogynists.

envfefe makes extensive use of the fefe module that provides type-safe and purely functional validation, sanitization and transformation.

Usage

Imagine you use the following environment variables, e.g., in a Docker .env file:

ELASTIC_HOST=elasticsearch
ELASTIC_PORT=9200
ENABLE_CACHE=true
LAUNCH_DATE=2017-12-08T10:00:00.000Z
GCLOUD_CREDENTIALS={"apiKey": "XYZ"}
WHITELIST=ada,john

Then you can use envfefe for parsing and sanitizing these into an object that you can use in your application:

import { parseEnv } from 'envfefe'
import { parseBoolean, parseDate, parseJson, parseNumber, pipe, string, success } from 'fefe'

const config = parseEnv({
  elasticHost: string(),
  elasticPort: pipe(string()).pipe(parseNumber()),
  enableCache: pipe(string()).pipe(parseBoolean()),
  launchDate: pipe(string()).pipe(parseDate()),
  gcloudCredentials: pipe(string()).pipe(parseJson()),
  whitelist: pipe(string()).pipe(value => success(value.split(','))),
})

If validation passes (check via isSuccess(config)) then config.right will equal:

{
  elasticHost: 'elasticsearch',
  elasticPort: 9000,
  enableCache: true,
  launchDate: Date('2017-12-08T10:00:00.000Z'),
  gcloudCredentials: {apiKey: 'XYZ'},
  whitelist: ['ada', 'john']
}

This module comes with full TypeScript support so if you are using TypeScript then config.right will have the correct types automatically:

{
  elasticHost: string
  elasticPort: number
  enableCache: boolean
  launchDate: Date
  gcloudCredentials: unknown
  whitelist: string[]
}

Note:

• camelCase keys are automatically translated to SNAKE_CASE environment variable names.
• By default all variables are mandatory. See below for optional variables and default values.
• Values in the resulting object have proper types. If it can't be sanitized because of a wrong type (like providing foo for a number) then isSuccess(config) will be false and config.left contains the FefeError (see FefeError docs).

Advanced usage

Optional variables

const config = parse({
  elasticHost: optional(string())
});

Default values

const config = parse({
  elasticHost: defaultTo(string())
});