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environment

Azure Pipelines npm Codecov David PRs Welcome

Environment variable configuration for Node.js made easy.

The problem

A lot of applications need to ensure that some environment variables are set from the beginning, and checking if the value in process.env is undefined every time is needed gets tedious very fast.

environment allows applications to ensure required env variables are set and are valid according to your definition of valid. See how to use it.

Table of Contents

Installation

With Yarn:

yarn add @strattadb/environment

or with npm:

npm install @strattadb/environment

Usage

An example env.js file:

// env.js

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  nodeEnv: {
    parser: parsers.whitelist(['production', 'development', 'test']),
    required: true,
    envVarName: 'NODE_ENV',
  },
  port: {
    parser: parsers.port,
    required: false,
    defaultValue: 4000,
    envVarName: 'PORT',
  },
});

export default env;

Now in a file:

// otherFile.js

import env from './env';

console.log(env.nodeEnv); // development
console.log(typeof env.nodeEnv); // string

console.log(env.port); // 4000
console.log(typeof env.port); // number

Examples

API

makeEnv(schema: Schema, processEnv?: { [key: string]: string | undefined }): Env

Ensures required env variables are present and returns an env object.

Supports passing a processEnv object as the second argument. If it's not passed, it uses process.env. This object will be used to look up the environment variables.

  • Schema:

    • [key: string]: object - The key will be accessible in the returning env object.
      • parser: function - A function that takes a string and can return anything. The return value will be accesible in env[key]. If the argument is not valid, it should throw.
      • required: boolean - Whether or not the env variable is required. If the value true and the env variable is not set, it'll throw. If the value is false it'll look for the env variable in process.env, if isn't set, it'll use defaultValue.
      • defaultValue: any? - Only valid if required: false. This is the default value of the env variable if it's not set. It won't be parsed or validated.
      • envVarName: string - The name of the env variable to look up (process.env[envVarName]).
      • description: string? - Helper text describing the variable.

  • Env:

    • [key: string]: any - The keys are the same as the ones in the schema.

Parsers

parsers.string(value: string): string

Trivial parser. It doesn't do any validation.

parsers.boolean(value: string): boolean

Ensures the value is a truthy or falsy value.

Truthy values: 'true', '1', 'yes', 'on'.

Falsy values: 'false', '0', 'no', 'off'.

parsers.integer(value: string): number

Ensures the value is an integer.

parsers.float(value: string): number

Ensures the value is a float.

parsers.email(value: string): string

Ensures the value is an email.

parsers.url(value: string): string

Ensures the value is a url.

parsers.ipAddress(value: string): string

Ensures the value is an IP address.

parsers.port(value: string): number

Ensures the value is a port.

parsers.whitelist(whitelistedValues: string[]): Parser<string>

Takes a list of valid values and returns a parser that ensures the value is in the whitelist.

Example:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  color: {
    parser: parsers.whitelilst(['red', 'blue', 'green']),
    required: true,
    envVarName: 'COLOR',
  },
});

parsers.regex(pattern: Regex): Parser<string>

Takes a regex and returns a parser that ensures the value matches the pattern.

Example:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  color: {
    parser: parsers.regex(/^green$/),
    required: true,
    envVarName: 'COLOR',
  },
});

parsers.array<T>({ parser: Parser<T>, separator?: string }): Parser<T>

Takes a parser and returns a parser that parses a list of values. The default value separator is ,.

Example:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  color: {
    parser: parsers.array({ parser: parsers.integer }),
    required: true,
    envVarName: 'FAVORITE_NUMBERS',
  },
});

parsers.positiveInteger(value: string): number

Ensures the value is a positive integer.

parsers.nonPositiveInteger(value: string): number

Ensures the value is a non-positive integer.

parsers.negativeInteger(value: string): number

Ensures the value is a negative integer.

parsers.nonNegativeInteger(value: string): number

Ensures the value is a non-negative integer.

Recipes

Making environment variables required

If required is true and the environment variable isn't set, it'll throw:

// env.js

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  notSet: {
    parser: parsers.string,
    required: true,
    envVarName: 'NOT_SET',
  },
});
node env.js

EnvironmentVariableError: NOT_SET is required but is not set
    at ...
    ...

Specifying a default value for when the env variable is not required

If the env variable is not required you must specify a default value:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  port: {
    parser: parsers.port,
    required: false,
    defaultValue: 4000,
    envVarName: 'PORT',
  },
});

console.log(env.port); // 4000

Providing a custom parser

A parser function must take a string value and can return anything. The value you return is what you'll get in the env object. If the value is not valid you should throw an error:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv({
  someValue: {
    parser: (value) => {
      if (value === 'forbiddenValue') {
        throw new Error('value is forbidden');
      }

      return value;
    },
    required: true,
    envVarName: 'SOME_VALUE',
  },
});

Usage with Dotenv

A common pattern is to load the env variables from a file using dotenv and then ensuring that the required variables are actually present:

const dotenv = require('dotenv');

dotenv.config(); // Loads env variables from `.env` file to `process.env`.

const { makeEnv, parsers } = require('@strattadb/environment');

const env = makeEnv({
  secretToken: {
    parser: parsers.string,
    required: true,
    envVarName: 'SECRET_TOKEN',
  },
});

Providing your own processEnv object

By default, makeEnv uses process.env to look up and get environment variables, but you can pass you own processEnv object as the second argument that will be used instead of process.env:

import { makeEnv, parsers } from '@strattadb/environment';

const env = makeEnv(
  {
    hello: {
      parser: parsers.string,
      required: true,
      envVarName: 'HELLO',
    },
  },
  {
    HELLO: 'WORLD',
  },
);

FAQ

Where should I call makeEnv in my application?

The best place to create the env object is very early in your application startup. Everything before you call makeEnv with your schema will not be guaranteed to have your required env variables.

Does it support changing env variables dynamically?

No, when you create an env object it will read the value of process.env at that time. After that, if anything makes changes to process.env, it will not be reflected in the env object.

Can I use the debug module with environment?

Yes! Set DEBUG=environment.

Can I have more than one env object per application?

Yes! You can have as many env objects as you want!

Node.js support

Node.js version 12 or higher. Every version of this library is tested in Node.js 12, 14 and 16.

Contributing

PRs, feature requests, bug reports, and any kind of contributions are welcome! See CONTRIBUTING.md.

Maintainers

Who's using environment

Related libraries

License

MIT