node-env-schema

Type-safe Environment Variable Validator for Node.js, Serverless, and other process.env based platforms

✨ Introduction

node-env-schema helps you validate, parse, and type your environment variables at runtime with TypeScript support.

It ensures that your environment variables are:

• Present (or use sensible defaults)
• Correctly typed (string, number, boolean, url, uri, port, or enum-like arrays)
• Type-safe and autocompleted in your IDE
• Ready for production and fail early if misconfigured

⚡ It works only in environments where process.env is available — like Node.js, Serverless, backend services, etc.

🛑 It does NOT work directly inside the browser (e.g., pure Vite frontends) unless you expose environment variables at build time.

📦 Installation

npm install node-env-schema

or

yarn add node-env-schema

🚀 Quick Start

// env.ts
import { defineEnv, validateEnv } from 'node-env-schema';

const schema = defineEnv({
  NODE_ENV: ['development', 'production', 'test'],
  PORT: { type: 'port', default: 3000 },
  DATABASE_URL: 'url',
  ENABLE_FEATURE: { type: 'boolean', default: false },
});

export const env = validateEnv(schema);

✅ env will now be a fully typed and validated object.

🛠 Usage Example

import { env } from './env';

console.log(env.NODE_ENV); // 'development' | 'production' | 'test'
console.log(env.PORT); // number
console.log(env.DATABASE_URL); // string (validated URL)
console.log(env.ENABLE_FEATURE); // boolean

If any environment variable is missing, incorrectly typed, or invalid, node-env-schema will throw an error at runtime, helping you catch configuration issues early.

📑 API Reference

defineEnv(schema)

Defines the environment schema.

• Accepts a schema object.
• Each key can either be:
  • A base type (string, number, boolean, url, uri, port)
  • An array of allowed strings (enum-like behavior)
  • An object { type: EnvType, default?: any } to specify default values

validateEnv(schema)

• Reads environment variables from process.env.
• Validates types.
• Applies default values where needed.
• Throws detailed errors if anything is missing or invalid.
• Returns a fully typed object.

📚 Supported Types

| Type | Validation Details | | ---------- | ---------------------------------------------------------- | | string | Any non-empty string | | number | Parsed as a number, throws if invalid | | boolean | Only accepts 'true' or 'false' | | url | Validated using URL constructor | | uri | Loosely validated URI format (scheme:rest) | | port | Integer between 0 and 65535 | | string[] | Restricts value to one of the given allowed strings (enum) |

⚙️ Advanced Example

import { defineEnv, validateEnv } from 'node-env-schema';

const schema = defineEnv({
  API_URL: 'url',
  NODE_ENV: ['development', 'production', 'test'],
  DEBUG_MODE: { type: 'boolean', default: false },
  TIMEOUT: { type: 'number', default: 5000 },
  SERVICE_PORT: 'port',
});

export const env = validateEnv(schema);

console.log(env.API_URL); // Valid URL string
console.log(env.NODE_ENV); // 'development' | 'production' | 'test'
console.log(env.DEBUG_MODE); // true or false
console.log(env.TIMEOUT); // number
console.log(env.SERVICE_PORT); // number (valid port)

If process.env.API_URL is invalid or missing, your application will immediately fail with a clear error like:

Expected environment variable API_URL to be a valid URL, but got "invalid-url"

🧠 Important Notes

• This package expects process.env to be available.
• Works perfectly with:
  • Node.js applications
  • Serverless functions (AWS Lambda, Vercel, Netlify, etc.)
  • Backend APIs
• ❗ It does NOT work automatically inside browser environments (like Vite client-side apps) unless you expose env variables at build time.

Example for Vite (build-time):

// vite.config.ts
define: {
  'process.env': process.env, // manually inject environment variables
}

🛡️ Error Handling Best Practices

You should call validateEnv at the very beginning of your app (before connecting to databases, starting servers, etc.).

Example:

import { env } from './env';

// Safe to continue after validation
startServer(env.PORT);

🔥 Error Examples

Missing variable

Error: Missing required environment variable: DATABASE_URL

Invalid number

Error: Expected environment variable PORT to be a number, but got "abc"

Invalid URL

Error: Expected environment variable API_URL to be a valid URL, but got "not_a_url"

Invalid enum value

Error: Expected environment variable NODE_ENV to be one of [development, production, test], but got "staging"

📜 License

MIT License © 2025 Sayantan Ghosh

🌟 Support the project

If you like node-env-schema, consider giving it a ⭐ on GitHub!