strict-env

Enforce 12-factor app environment variables in development or production

Recommended usage

1. Create .env following dotenv formatting. Make sure to add it to your .gitignore file. Recommended to commit dummy values in a file example.env as well.
2. npm i -E strict-env
3. In config.js (or similar):

const env = require('strict-env');

/*
 * The `config` function expects a mapping of required environment
 * variables names to transformer functions. The library provides
 * transformers for common use cases, but you can easily provide
 * your own.
 */
module.exports = env.config({
  BOOLEAN: env.boolean, // Allows values: 'true', 'false', '1', '0'
  INTEGER: env.integer,
  JSON: env.json,       // Any valid input for `JSON.parse`
  NUMBER: env.number,
  PORT: env.port,
  STRING: env.string,   // Non-empty string

  /*
   * Custom transformers must either return the transformed value
   * or throw an error. They are invoked with two parameters:
   * value - String value of environment variable, or `undefined`
   *         if not set. (This allows you to specify variables that
   *         are optional or have default values.)
   * name - String name of the target environment variable. You
   *        sholud use this to generate nice error messages.
   */
  CUSTOM: (value, name) => {
    if (/\d+/.test(value)) {
      return Number(value);
    } else {
      const message =
        `Env. var. should be a non-negative integer: "${name}"`;
      throw new Error(message);
    }
  },
});

// You can also use the `get` function to process single variables.
// This is useful for ES modules!
export const PORT = env.get('PORT', env.port);

4. Use config values in other files:

const config = require('./config');

console.info(config.CUSTOM); // Will be be a non-negative integer
console.info(config.PORT);   // Will be be a valid port number
console.info(config.STRING); // Will be be a non-empty string
// Etc.

// Or use ES modules
import { PORT } from './config';

Compatibility

This library should work with node versions as old as 0.10, thanks to Rollup and Babel. (Please file an issue if that is not the case!)