env-safe-check

Zero-dependency, type-safe environment validation for Node.js & TypeScript

✨ What is env-safe-check?

env-safe-check is a lightweight, zero-dependency library that validates environment variables at application startup.

It ensures your app:

• 🚨 Fails fast when required variables are missing
• 🎯 Validates types (string, number, boolean, json)
• 🧠 Supports custom validators with helpful hints
• 🧩 Provides defaults for optional variables
• 🎨 Outputs clean, CLI-friendly error messages
• 🔒 Is CI-safe (non-zero exit on validation failure)

Stop debugging production issues caused by misconfigured environment variables.

🚀 Quick Start

Install

npm install env-safe-check
# or
yarn add env-safe-check
# or
pnpm add env-safe-check

⚡ TL;DR (Recommended Schema Mode)

import { validateEnv } from 'env-safe-check';

export const env = validateEnv({
  schema: {
    DATABASE_URL: {
      type: 'string',
      description: 'PostgreSQL connection URL',
    },

    PORT: {
      type: 'number',
      default: '3000',
    },

    DEBUG: {
      type: 'boolean',
      required: false,
      default: 'false',
    },

    NODE_ENV: {
      type: 'string',
      validator: (value) =>
        ['development', 'production', 'test'].includes(value)
          ? true
          : 'Must be one of: development, production, test',
      validatorHint: 'development | production | test',
    },

    FEATURE_FLAGS: {
      type: 'json',
      required: false,
    },
  },
});

console.log(env.PORT); // number

CLI Companion

You can run validation without importing the library in app code:

# with .env loading
npx env-safe-check validate --schema ./env.schema.js --env-file ./.env

This is useful for CI preflight checks and npm scripts:

{
  "scripts": {
    "validate:env": "env-safe-check validate --schema ./env.schema.js"
  }
}

CLI options

| Option | Description | |--------|-------------| | validate | Validate env variables using a schema module | | --schema <path> | Path to a module that exports schema (default, schema, or envSchema) | | --env-file <path> | Load env vars from file before validation | | --silent | Suppress non-error output |

Schema file example:

export default {
  DATABASE_URL: {
    type: "string",
    description: "PostgreSQL connection URL",
  },
  PORT: {
    type: "number",
    default: "3000",
  },
};

Note: TypeScript schema files (.ts) are not loaded directly by the CLI on Node.js 20. Use .js/.mjs output or run with a TypeScript loader.

🧩 Why env-safe-check?

Many apps rely on process.env directly.

That leads to:

• ❌ Missing variables discovered in production
• ❌ Silent failures
• ❌ Wrong data types ("3000" instead of 3000)
• ❌ Unclear error messages
• ❌ Configuration drift across environments

env-safe-check solves this by validating everything at startup — clearly, strictly, and predictably.

🛠 API

1️⃣ Schema Mode (Recommended)

validateEnv(config: ValidateEnvOptions): Record<string, any>

Options

| Option | Description | |---------------|-------------| | schema | Object defining environment variables and their validation rules | | silent | Default: false. If true, suppresses output and does not throw |

Returns

Parsed and validated environment variables.

Throws

EnvValidationError (when silent: false and validation fails)

2️⃣ Simple Mode (Legacy)

validateEnv(required: string[]): void

Example:

validateEnv(['DATABASE_URL', 'API_KEY']);

• Exits process with code 1 if any are missing
• Prints colorful CLI messages

🧠 Variable Schema

interface VariableSchema {
  type?: 'string' | 'number' | 'boolean' | 'json';
  required?: boolean;        // default: true
  default?: string;
  validator?: (value: string) => boolean | string;
  validatorHint?: string;
  description?: string;
}

🎯 Advanced Examples

Custom Validator with Hint

validateEnv({
  schema: {
    WORKER_THREADS: {
      type: 'number',
      validator: (value) => {
        const num = Number(value);
        return num >= 1 && num <= 32
          ? true
          : 'Must be between 1 and 32';
      },
      validatorHint: 'integer between 1 and 32',
      description: 'Worker pool size',
    },
  },
});

Handling Errors Explicitly

import { validateEnv, EnvValidationError } from 'env-safe-check';

try {
  validateEnv({ schema: { DB_URL: 'string' } });
} catch (err) {
  if (err instanceof EnvValidationError) {
    console.error('Missing:', err.missing);
    console.error('Invalid:', err.invalid);
  }
}

🧪 Best Practices

• ✅ Validate once at application startup
• ✅ Always include description for team clarity
• ✅ Provide validatorHint for custom validators
• ✅ Keep silent: false in production
• ✅ Explicitly mark optional variables with required: false

⚠️ Troubleshooting

| Issue | Fix | |-------|-----| | Boolean parsing fails | Use true, false, 1, or 0 | | Number parsing fails | Ensure numeric string (e.g., 3000) | | JSON parsing fails | Provide valid JSON ({"enabled": true}) | | Default not applied | Must set required: false |

🏗 Project Structure (For Contributors)

• Source: src/ (TypeScript)
• Output: dist/ (ESM)

Scripts

npm run build
npm run typecheck
npm test

📦 Publishing

1. Bump version in package.json
2. npm run build
3. Verify main and types
4. npm publish --access public

🤝 Contributing

Issues and PRs are welcome.

Before submitting:

• Run type checks
• Ensure tests pass
• Keep changes focused and minimal