✨ Features

• 🔧 Automatic Type Detection - Runtime types inferred from fallback values
• 🔗 Template Variables - ${VAR} syntax with circular reference protection
• 🎯 Class Properties - Functional and Decorator-based configuration for class members (Decorators: TypeScript only)
• 🏷️ Built-in & Custom Converters - Ready-to-use converters for common patterns + custom transformations
• 🔖 Tagged Template Resolver - Tagged template literals with environment variable resolution
• 🌍 Environment Detection - Built-in development/staging/production handling
• 💪 Edge Case Handling - Robust validation and parsing for all scenarios
• 🛡️ Type Safety - Full TypeScript support with proper type inference (TypeScript optional)
• 📂 Multiple .env Files - Load from multiple sources
• ⚡ Lightweight - Minimal overhead with dotenv bundled

Table of Contents

⚙️ Essentials

• Requirements
• Quick Start
  • Installation
  • Basic Usage

🧬 API Reference

• API Reference
  • Decorator API
    • Modern Syntax (Recommended)
    • Classic Syntax
    • Automatic Runtime Type Detection
    • Primitive Converters
    • Built-in Converters
    • Custom Array Converters
    • Custom Converters
    • Handling Missing Values
  • Functional API
  • Tagged Template Resolver
  • Converter Type Quick Reference

🌍 Environment & Templates

• Environment Detection
  • Environment Management
• Template Variables
  • Circular Reference Protection

🛠 Configuration & Errors

• Configuration
  • Multiple .env Files
  • Dotenv Configuration
• Error Handling
  • Error Code Reference

🚀 Examples

• Advanced Examples
  • JavaScript
  • TypeScript

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Requirements

TypeScript Users Only

• TypeScript: >=5.8 (Only required for decorator API)

// tsconfig.json (required settings for decorators)
{
  "experimentalDecorators": true,
  "module": "esnext", // or "nodenext"
  "moduleResolution": "bundler", // or "nodenext"
  "target": "ESNext",
  "lib": ["ESNext"]
}

[!NOTE] JavaScript users can use all features except the @Envapt decorator API. The Functional API, Tagged Template Resolver, and all converters work perfectly in plain JavaScript.

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Quick Start

Installation

| Package Manager | Command | | --------------- | --------------------------------- | | pnpm | pnpm add envapt | | yarn | yarn add envapt | | npm | npm install envapt | | deno (jsr) | deno add jsr:@materwelon/envapt | | deno (npm) | deno add npm:envapt | | bun | bun add envapt |

Basic Usage

Step 1: Create a .env file:

APP_PORT=8443
APP_URL=http://localhost:${APP_PORT}
DATABASE_URL=postgres://localhost:5432/mydb
IS_PRODUCTION=false
MAX_CONNECTIONS=100
ALLOWED_ORIGINS=https://app.com,https://admin.com

JavaScript Example (Functional API):

import { Envapter, Converters } from 'envapt';

// Basic usage
const port = Envapter.getNumber('APP_PORT', 3000);
const url = Envapter.get('APP_URL', 'http://localhost:3000');
const isProduction = Envapter.isProduction;

console.log(`Server running on port ${port}`); // 8443
console.log(`URL: ${url}`); // "http://localhost:8443"

// Advanced converters
const corsOrigins = Envapter.getUsing('ALLOWED_ORIGINS', Converters.Array, []);
const dbConfig = Envapter.getUsing('DATABASE_CONFIG', Converters.Json, {});

// Tagged template literals
const message = Envapter.resolve`Server ${'APP_URL'} is ready!`;
console.log(message); // "Server http://localhost:8443 is ready!"

TypeScript Example (Decorator API):

import { Envapt, Envapter, Converters } from 'envapt';

// Global app configuration (static properties)
class AppConfig extends Envapter {
  @Envapt('APP_PORT', 3000)
  static readonly port: number;

  // The Classic Syntax only works for Primitive Converters. Converters.Url is a Built-in Converter.
  @Envapt('APP_URL', { fallback: new URL('http://localhost:3000'), converter: Converters.Url })
  static readonly url: URL;

  @Envapt('ALLOWED_ORIGINS', {
    fallback: ['http://localhost:3000'],
    converter: Converters.Array
  })
  static readonly allowedOrigins: string[];
}

// Service configuration (instance properties)
class DatabaseService {
  @Envapt('DATABASE_URL', 'sqlite://memory')
  declare readonly databaseUrl: string;

  // Will detect that '10' is a number and set the runtime type accordingly
  @Envapt('MAX_CONNECTIONS', 10)
  declare readonly maxConnections: number;

  @Envapt('REQUEST_TIMEOUT', { converter: Converters.Time, fallback: 5000 })
  declare readonly timeout: number; // Converts "5s" to 5000ms

  async connect() {
    console.log(`Connecting to ${this.databaseUrl}`);
    // Connection logic here
  }
}

// Usage
console.log(AppConfig.port); // 8443 (number)
console.log(AppConfig.url.href); // "http://localhost:8443"

const dbService = new DatabaseService();
await dbService.connect();

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API Reference

Decorator API

[!IMPORTANT] TypeScript Only: The @Envapt decorator API requires TypeScript with experimentalDecorators: true. JavaScript users should use the Functional API instead.

The @Envapt decorator can be used on both static and instance class properties:

• Static properties: Can use for global configuration that's shared across your entire application (e.g., app port, global features, environment settings)
• Instance properties: Can use for service-specific configuration that may vary per service or when you want the configuration tied to a specific class instance (e.g., database connections, service endpoints, per-service settings)

Important: Instance properties must be declared with declare keyword or ! assertion since they're populated by the decorator rather than set in a constructor.

Modern Syntax (Recommended)

@Envapt('ENV_VAR', { fallback?: T, converter?: EnvConverter<T> })

[!TIP] Generic Typing for Better IntelliSense

You can specify explicit types using generics for better type safety and IntelliSense:

// Explicit typing provides better IntelliSense for complex types
@Envapt<DatabaseConfig>('DB_CONFIG', {
  fallback: { host: 'localhost', port: 5432, ssl: false },
  converter: Converters.Json
})
static readonly dbConfig: DatabaseConfig;

Classic Syntax

@Envapt('ENV_VAR', fallback?, converter?)

Automatic Runtime Type Detection

Types are automatically inferred from fallback values.

class Config extends Envapter {
  // Static properties for global settings
  @Envapt('APP_NAME', 'MyApp') // string
  static readonly appName: string;

  @Envapt('APP_PORT', 3000) // number
  static readonly port: number;

  @Envapt('DEBUG_MODE', false) // boolean
  static readonly debugMode: boolean;

  // Instance properties for service-specific settings
  @Envapt('SMTP_HOST', 'localhost') // string
  declare readonly smtpHost: string;

  @Envapt('SMTP_PORT', 587) // number
  declare readonly smtpPort: number;

  @Envapt('SMTP_SECURE', true) // boolean
  declare readonly smtpSecure: boolean;

  sendEmail(to: string, subject: string) {
    console.log(`Sending via ${this.smtpHost}:${this.smtpPort}`);
  }
}

Primitive Converters

Envapt allows using the 5 "primitive" type-like converters. These will coerce values.

[!NOTE] The runtime validator will ignore this usage, allowing type coercion for flexibility.

Valid Primitive Types: String, Number, Boolean, Symbol, and BigInt.

class Config extends Envapter {
  @Envapt('PORT_STRING', { fallback: 'hello-world', converter: String })
  static readonly portAsString: string;

  @Envapt('DEBUG_FLAG', { fallback: true, converter: Boolean })
  static readonly debugMode: boolean;

  @Envapt('USER_ID', { fallback: 12345, converter: Number })
  static readonly userId: number;

  @Envapt('MAX_SAFE_INT', { fallback: 9007199254740991n, converter: BigInt })
  static readonly maxSafeInt: bigint;

  @Envapt('APP_INSTANCE', { fallback: Symbol(main), converter: Symbol })
  static readonly appInstance: symbol;

  // Instance properties work the same way
  @Envapt('CONNECTION_TIMEOUT', { fallback: 5000, converter: Number })
  declare readonly timeout: number;

  // Type coercion example
  @Envapt('PERMISSIONS', { fallback: '72394823472342983', converter: BigInt })
  declare readonly permissions: bigint; // Converts "72394823472342983" to BigInt
}

When to use primitive converters:

• When you need explicit type coercion between incompatible types
• When working with external systems that provide values in unexpected formats

Built-in Converters

Envapt provides many built-in converters for common patterns:

[!IMPORTANT] Use the Converters enum instead of string literals. They look better, and provide better type inference:

import { Converters } from 'envapt';
// ✅ Recommended: Use enum
@Envapt('PORT', { converter: Converters.Number, fallback: 3000 })

// ❌ Discouraged: String literals (still supported for compatibility)
@Envapt('PORT', { converter: 'number', fallback: 3000 })

Built-in converters enforce strict type validation between the converter and fallback types. The converter's expected return type must match the fallback's type.

class Config extends Envapter {
  // Basic types
  @Envapt('APP_NAME', { converter: Converters.String, fallback: 'MyApp' })
  static readonly appName: string;

  @Envapt('PORT', { converter: Converters.Number, fallback: 3000 })
  static readonly port: number;

  @Envapt('PRODUCTION_MODE', { converter: Converters.Boolean, fallback: false })
  static readonly productionMode: boolean;

  // Advanced types
  @Envapt('CORS_ORIGINS', { converter: Converters.Array, fallback: [] })
  static readonly corsOrigins: string[];

  @Envapt('CONFIG_JSON', { converter: Converters.Json, fallback: {} })
  static readonly config: object;

  @Envapt('API_URL', { converter: Converters.Url, fallback: new URL('http://localhost') })
  static readonly apiUrl: URL;

  @Envapt('TIMEOUT', { converter: Converters.Time, fallback: 5000 })
  static readonly timeout: number; // Converts "30s" to 30000ms

  // Instance properties work the same way
  @Envapt('CACHE_TTL', { converter: Converters.Time, fallback: 3600000 })
  declare readonly cacheTtl: number; // "1h" becomes 3600000ms
}

[!WARNING] These will throw runtime errors due to type mismatches:

// ❌ String converter with number fallback
@Envapt('VAR', { converter: Converters.String, fallback: 42 })

// ❌ URL converter with string fallback
@Envapt('VAR', { converter: Converters.Url, fallback: 'http://example.com' })

// ✅ Use primitive constructors for type coercion instead
@Envapt('VAR', { converter: String, fallback: 42 })

Available Built-in Converters:

| Converter | Alias | Description | | -------------------- | ----------- | -------------------------------------------------------------------- | | Converters.String | 'string' | String values | | Converters.Number | 'number' | Numeric values (integers and floats) | | Converters.Integer | 'integer' | Integer values only | | Converters.Float | 'float' | Float values only | | Converters.Boolean | 'boolean' | Boolean values (true/false, yes/no, on/off, 1/0) | | Converters.Bigint | 'bigint' | BigInt values for large integers | | Converters.Symbol | 'symbol' | Symbol values (creates symbols from string descriptions) | | Converters.Json | 'json' | JSON objects/arrays (safe parsing with fallback) | | Converters.Array | 'array' | Comma-separated string arrays | | Converters.Url | 'url' | URL objects | | Converters.Regexp | 'regexp' | Regular expressions (supports /pattern/flags syntax) | | Converters.Date | 'date' | Date objects (supports ISO strings and timestamps) | | Converters.Time | 'time' | Time values (e.g. "5s", "30m", "2h" converted to milliseconds) |

Custom Array Converters

For more control over array parsing:

[!IMPORTANT] Array converters validate that:

1. Fallback must be an array (if provided)
2. All fallback elements have consistent types (no mixed types like ['string', 42, true])
3. Array converter type matches fallback element types (if type is specified)

class Config extends Envapter {
  // Basic array (comma-separated strings)
  @Envapt('TAGS', { converter: Converters.Array, fallback: [] })
  static readonly tags: string[];

  // Custom delimiter
  @Envapt('ALLOWED_METHODS', { converter: { delimiter: '|' }, fallback: ['GET'] })
  declare readonly allowedMethods: string[];

  // Custom delimiter with type conversion
  @Envapt('RATE_LIMITS', { converter: { delimiter: ',', type: Converters.Number }, fallback: [100] })
  declare readonly rateLimits: number[];

  @Envapt('FEATURE_FLAGS', { converter: { delimiter: ';', type: 'boolean' }, fallback: [false] })
  declare readonly featureFlags: boolean[];
}

[!WARNING] These will throw runtime validation errors:

// ❌ Mixed types in fallback array
@Envapt('MIXED', { converter: Converters.Array, fallback: ['string', 42, true] })

// ❌ Array converter type doesn't match fallback elements
@Envapt('NUMS', { converter: { delimiter: ',', type: Converters.Number }, fallback: ['not', 'numbers'] })

// ❌ Non-array fallback with array converter
@Envapt('INVALID', { converter: Converters.Array, fallback: 'not-an-array' })

ArrayConverter Interface:

• delimiter: string - The string used to split array elements
• type?: BuiltInConverter - Optional type to convert each element to (excludes Converters.Array, Converters.Json, and Converters.Regexp)

Custom Converters

Transform environment values to any type:

class Config extends Envapter {
  @Envapt('TAGS', {
    fallback: new Set(['default']),
    converter: (raw, fallback) => {
      if (!raw) return fallback;
      return new Set(raw.split(',').map((s) => s.trim()));
    }
  })
  static readonly tags: Set<string>;

  @Envapt('NOTIFICATION_CHANNELS', {
    fallback: new Map([['email', 'enabled']]),
    converter: (raw, fallback) => {
      if (!raw) return fallback;
      const map = new Map();
      raw.split(',').forEach((pair) => {
        const [key, value] = pair.split(':');
        map.set(key?.trim(), value?.trim() || 'enabled');
      });
      return map;
    }
  })
  declare readonly channels: Map<string, string>;
}

[!TIP] Custom Validation with Error Throwing

Custom converters can throw errors for validation. The custom converter is called even when a variable is not found in the env file(s):

@Envapt<string>('API_KEY', {
  converter(raw, _fallback) {
    if (typeof raw !== 'string' || raw === '') {
      throw new Error('API_KEY is required and cannot be empty');
    }
    return raw;
  }
})
static readonly apiKey: string;

No fallback needed here because the converter throws an error if a value is not what we want it to be

Handling Missing Values

Control what happens when environment variables don't exist:

class Config extends Envapter {
  // Returns undefined if not found
  @Envapt('OPTIONAL_FEATURE', { fallback: undefined })
  static readonly optionalFeature: string | undefined;

  // Returns null if not found (no fallback provided)
  @Envapt('MISSING_CONFIG', { converter: Converters.String })
  static readonly missingConfig: string | null;

  // Uses fallback if not found
  @Envapt('DEFAULT_THEME', { fallback: 'light' })
  static readonly defaultTheme: string;

  // Instance properties work the same way
  @Envapt('LOG_FILE_PATH', { fallback: undefined })
  declare readonly logFilePath: string | undefined;
}

Functional API

For functional-style environment variable access on primitive types:

import { Envapter, Converters } from 'envapt';

// Basic type-specific getters
const str = Envapter.get('STRING_VAR', 'default');
const num = Envapter.getNumber('NUMBER_VAR', 42);
const bool = Envapter.getBoolean('BOOLEAN_VAR', false);
const bigint = Envapter.getBigInt('BIGINT_VAR', 100n);
const symbol = Envapter.getSymbol('SYMBOL_VAR', Symbol('default'));

// Advanced converter methods
const jsonData = Envapter.getUsing('CONFIG_JSON', Converters.Json);
const urlArray = Envapter.getUsing('API_URLS', { delimiter: ',', type: Converters.Url });
const customData = Envapter.getWith('RAW_DATA', (raw) => raw?.split('|').map((s) => s.trim()));

// Instance methods (same API available)
const envapter = new Envapter();
const value = envapter.get('VAR', 'default');
const processed = envapter.getUsing('DATA', Converters.Array);

For functional-style environment variable access with converters:

import { Envapter, Converters } from 'envapt';

// Use built-in converters directly
const config = Envapter.getUsing('API_CONFIG', Converters.Json, { default: 'value' });
const urls = Envapter.getUsing('SERVICE_URLS', { delimiter: '|', type: Converters.Url });

// TypeScript: Use type override for better type inference
const typedConfig = Envapter.getUsing<{ host: string; port: number; ssl: boolean }>('DATABASE_CONFIG', Converters.Json);
// typedConfig is now typed as { host: string; port: number; ssl: boolean } instead of JsonValue | undefined

// Use custom converter functions
const processedData = Envapter.getWith(
  'RAW_DATA',
  (raw, fallback) => {
    if (!raw) return fallback ?? [];
    return raw.split(',').map((item) => ({ name: item.trim(), enabled: true }));
  },
  []
);

// Instance methods work the same way
const envapter = new Envapter();
const result = envapter.getUsing('DATABASE_CONFIG', Converters.Json);

[!TIP] Type Override with getUsing

You can explicitly specify the return type for getUsing when TypeScript's inference isn't specific enough (especially useful with Converters.Json):

// Default behavior
const config = Envapter.getUsing('CONFIG', Converters.Json); // type: JsonValue | undefined (undefined because no fallback)

// Override with specific interface
interface DatabaseConfig {
  host: string;
  port: number;
  ssl: boolean;
}
const dbConfig = Envapter.getUsing<DatabaseConfig>('DB_CONFIG', Converters.Json);
// dbConfig is now properly typed as DatabaseConfig

Make sure the fallback value matches the expected type, if you use a fallback. Otherwise you'll see a TypeScript error.
This does NOT validate the type at runtime. You'll need to handle that yourself.

Converter Type Quick Reference

| Use Case | Converter Type | Example | | ----------------------- | ------------------------- | --------------------------------------------------------- | | Type coercion | Primitive constructors | converter: String | | Strict validation | Built-in converters | converter: Converters.String | | Array parsing | Built-in Array converters | converter: { delimiter: ',', type?: Converters.String } | | Complex transforms | Custom function | converter: (raw, fallback) => ... | | Functional built-in | getUsing() method | Envapter.getUsing('VAR', Converters.Json) | | Type override | getUsing<T>() method | Envapter.getUsing<MyType>('VAR', Converters.Json) | | Functional custom | getWith() method | Envapter.getWith('VAR', (raw) => transform(raw)) |

[!TIP] Use the Converters enum. They look better. Start with built-in converters, use primitive constructors when you need coercion, and custom converters for complex transforms.

Tagged Template Resolver

Envapt provides a convenient tagged template literal syntax for resolving environment variables directly in template strings:

import { Envapter } from 'envapt';

// Given these environment variables:
// API_HOST=api.example.com
// API_PORT=8080
// API_URL=https://${API_HOST}:${API_PORT}
// SERVICE_NAME=UserService

// Use tagged template literals for string interpolation
const endpoint = Envapter.resolve`Connecting to ${'SERVICE_NAME'} at ${'API_URL'}`;
// Returns: "Connecting to UserService at https://api.example.com:8080"

const logMessage = Envapter.resolve`Starting ${'SERVICE_NAME'} on port ${'API_PORT'}`;
// Returns: "Starting UserService on port 8080"

// Works with instance methods too
const envapter = new Envapter();
const status = envapter.resolve`${'SERVICE_NAME'} is running`;
// Returns: "UserService is running"

Works seamlessly with template variables in your .env file:

# Your .env file
API_HOST=api.example.com
API_PORT=8080
API_URL=https://${API_HOST}:${API_PORT}  # Template resolved first
SERVICE_NAME=UserService

const message = Envapter.resolve`Service ${'SERVICE_NAME'} endpoint: ${'API_URL'}`;
// Returns: "Service UserService endpoint: https://api.example.com:8080"

[!NOTE] Tagged template literals work with any environment variables, including those that use ${VAR} template syntax in your .env file. The template resolution happens first, then the tagged template interpolation.

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Environment Detection

Envapt automatically detects your environment from these variables (in order):

1. ENVIRONMENT
2. ENV
3. NODE_ENV

Supported values: development, staging, production (case-sensitive)

Environment Management

import { Envapter, EnvaptEnvironment } from 'envapt';

// Check current environment
console.log(Envapter.environment); // Environment.Development (default)
console.log(Envapter.isProduction); // false
console.log(Envapter.isDevelopment); // true
console.log(Envapter.isStaging); // false

// Set environment
Envapter.environment = EnvaptEnvironment.Production;
Envapter.environment = 'staging'; // string also works

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Configuration

Multiple .env Files

import { resolve } from 'node:path';
import { Envapter } from 'envapt';

// Load from multiple files
Envapter.envPaths = [resolve(import.meta.dirname, '.env.local'), resolve(import.meta.dirname, '.env.production')];

// Or single file
Envapter.envPaths = resolve(import.meta.dirname, '.env.production');

// Or just don't set a path for it to default to .env at the root of your project

// Also, in CommonJS, use `__dirname` instead of `import.meta.dirname`:

Dotenv Configuration

Envapt allows you to customize dotenv behavior by setting configuration options:

import { Envapter } from 'envapt';

// Set dotenv configuration options
Envapter.dotenvConfig = {
  encoding: 'latin1', // File encoding (default: 'utf8')
  debug: true, // Enable debug logging
  override: true, // Override existing environment variables
  quiet: false, // Suppress non-error output (default: true)
  DOTENV_KEY: 'key...' // Decryption key for .env.vault files
};

// Get current configuration
console.log(Envapter.dotenvConfig);

[!NOTE] The path and processEnv options are managed internally by Envapter and cannot be set via dotenvConfig.

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Template Variables

Envapt supports variable interpolation with ${VARIABLE} syntax:

DATABASE_HOST=localhost
DATABASE_PORT=5432
DATABASE_URL=postgres://${DATABASE_HOST}:${DATABASE_PORT}/mydb

API_VERSION=v1
API_BASE=https://api.example.com
API_ENDPOINT=${API_BASE}/${API_VERSION}/users

Circular Reference Protection

CIRCULAR_A=${CIRCULAR_B}
CIRCULAR_B=${CIRCULAR_A}

Circular references are detected and preserved as-is rather than causing infinite loops.

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Error Handling

Envapt provides detailed error codes for better debugging and error handling:

import { EnvaptError, EnvaptErrorCodes } from 'envapt';

try {
  // This will throw an error for invalid configuration
  Envapter.dotenvConfig = { path: '.env.custom' };
} catch (error) {
  if (error instanceof EnvaptError) {
    console.log('Error code:', error.code);
    console.log('Error message:', error.message);

    // Handle specific error types
    switch (error.code) {
      case EnvaptErrorCodes.InvalidUserDefinedConfig:
        console.log('Invalid configuration provided');
        break;
      case EnvaptErrorCodes.EnvFileNotFound:
        console.log('Environment file not found');
        break;
      default:
        console.warn('Unhandled error code:', error.code);
        break;
    }
  }
}

Error Code Reference

🔧 Fallback Errors (1xx)

| Error Code | Description | | ---------------------------------------- | --------------------------------------------------------- | | InvalidFallback (101) | Invalid fallback value provided | | InvalidFallbackType (102) | Fallback value type doesn't match expected converter type | | ArrayFallbackElementTypeMismatch (103) | Array fallback contains elements of wrong type | | FallbackConverterTypeMismatch (104) | Fallback type doesn't match the specified converter |

🧪 Converter Errors (2xx)

| Error Code | Description | | --------------------------------- | ---------------------------------------------- | | InvalidArrayConverterType (201) | Invalid array converter configuration provided | | InvalidBuiltInConverter (202) | Invalid built-in converter specified | | InvalidCustomConverter (203) | Custom converter function is invalid | | InvalidConverterType (204) | Converter type is not recognized | | PrimitiveCoercionFailed (205) | Primitive type coercion failed |

📂 Environment File & Config Errors (3xx)

| Error Code | Description | | -------------------------------- | ---------------------------------------------- | | MissingDelimiter (301) | Delimiter is missing in array converter config | | InvalidUserDefinedConfig (302) | Invalid user-defined configuration provided | | EnvFilesNotFound (303) | Specified environment file doesn't exist |

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Advanced Examples

JavaScript

import { Envapter, Converters } from 'envapt';

// Global configuration
const config = {
  port: Envapter.getNumber('PORT', 3000),
  requestTimeout: Envapter.getUsing('REQUEST_TIMEOUT', Converters.Time, 10000), // "5s" -> 5000ms
  featureFlags: Envapter.getWith(
    'FEATURE_FLAGS',
    (raw, fallback) => {
      if (!raw) return fallback;
      return new Set(raw.split(',').map((s) => s.trim()));
    },
    new Set(['basic'])
  )
};

// Service configuration
class DatabaseService {
  constructor() {
    this.databaseUrl = Envapter.get('DB_URL', 'sqlite://memory');
    this.cacheTtl = Envapter.getUsing('CACHE_TTL', Converters.Time, 3600000); // "1h" -> 3600000ms
    this.redisUrls = Envapter.getWith(
      'REDIS_URLS',
      (raw, fallback) => (raw ? raw.split(',').map((s) => new URL(s)) : fallback),
      [new URL('redis://localhost:6379')]
    );
  }

  async initialize() {
    console.log(`App running on port ${config.port}`);
    console.log(`Database: ${this.databaseUrl}`);
    console.log(`Cache TTL: ${this.cacheTtl}ms`);
  }
}

TypeScript

import { Envapt, Envapter, Converters } from 'envapt';

class AppConfig extends Envapter {
  // Global settings (static)
  @Envapt('PORT', 3000)
  static readonly port: number;

  @Envapt('REQUEST_TIMEOUT', { converter: Converters.Time, fallback: 10000 })
  static readonly requestTimeout: number; // "5s" -> 5000ms (if env is set to "5s")

  @Envapt('FEATURE_FLAGS', {
    fallback: new Set(['basic']),
    converter: (raw, fallback) => {
      if (!raw) return fallback;
      return new Set(raw.split(',').map((s) => s.trim()));
    }
  })
  static readonly featureFlags: Set<string>;

  // Service settings (instance)
  @Envapt('DB_URL', 'sqlite://memory')
  declare readonly databaseUrl: string;

  @Envapt('CACHE_TTL', { converter: Converters.Time, fallback: 3600000 })
  declare readonly cacheTtl: number; // "1h" -> 3600000ms

  @Envapt('REDIS_URLS', {
    fallback: [new URL('redis://localhost:6379')],
    converter: (raw, fallback) => (raw ? raw.split(',').map((s) => new URL(s)) : fallback)
  })
  declare readonly redisUrls: URL[];

  async initialize() {
    console.log(`App running on port ${AppConfig.port}`);
    console.log(`Database: ${this.databaseUrl}`);
    console.log(`Cache TTL: ${this.cacheTtl}ms`);
  }
}

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