tessl/npm-config

Configuration control for production node deployments

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Overview

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Files

Core Configuration

Name: tessl/npm-config
Author: tessl

Core configuration access providing the primary interface for retrieving and validating configuration values. Includes both method-based and direct property access with full validation support.

Capabilities

Configuration Access Methods

Primary methods for accessing configuration values with validation and error handling.

/**
 * Get configuration value by property path
 * @param property - Dot-notation path to configuration property (e.g., 'database.host')
 * @returns Configuration value of any type
 * @throws Error if property is null, undefined, or doesn't exist
 */
config.get(property: string): any;

/**
 * Test if configuration property exists
 * @param property - Dot-notation path to configuration property
 * @returns True if property is defined, false otherwise
 */
config.has(property: string): boolean;

Usage Examples:

const config = require('config');

// Basic property access
const dbHost = config.get('database.host');
const port = config.get('server.port');

// Nested property access
const credentials = config.get('services.api.credentials');

// Check existence before access
if (config.has('features.experimental')) {
  const experimental = config.get('features.experimental');
  console.log('Experimental features:', experimental);
}

// Error handling
try {
  const value = config.get('nonexistent.property');
} catch (error) {
  console.error('Configuration property not found:', error.message);
}

Direct Property Access

Direct access to configuration properties as object properties. All configuration objects inherit Config prototype methods.

// Direct property access (alternative to get() method)
config.propertyName: any;
config.nested.property: any;

// All configuration sub-objects have Config methods
config.database.get(property: string): any;
config.database.has(property: string): boolean;

Usage Examples:

const config = require('config');

// Direct property access
const appName = config.appName;
const dbConfig = config.database;

// Sub-configuration access
const dbHost = config.database.host;
const dbPort = config.database.port;

// Using Config methods on sub-objects
if (config.database.has('credentials')) {
  const credentials = config.database.get('credentials');
}

// Mixed access patterns
const serverConfig = config.get('server');
const serverHost = serverConfig.host; // Direct access on returned object
const serverPort = serverConfig.get('port'); // Method access on returned object

Configuration Value Types

Configuration values can be of any JavaScript type, with full support for nested objects and arrays.

// Supported configuration value types
type ConfigValue = 
  | string 
  | number 
  | boolean 
  | null 
  | object 
  | any[] 
  | ConfigValue[];

// Configuration objects maintain type information
interface ConfigObject {
  [key: string]: ConfigValue;
  get(property: string): ConfigValue;
  has(property: string): boolean;
}

Usage Examples:

// String values
const appName = config.get('app.name'); // "My Application"

// Number values  
const port = config.get('server.port'); // 3000
const timeout = config.get('timeout'); // 30.5

// Boolean values
const debugMode = config.get('debug'); // true

// Object values
const dbConfig = config.get('database');
// { host: 'localhost', port: 5432, name: 'myapp' }

// Array values
const allowedHosts = config.get('security.allowedHosts');
// ['localhost', '127.0.0.1', 'myapp.com']

// Nested arrays and objects
const services = config.get('services');
// { api: { url: '...', timeout: 5000 }, cache: { enabled: true } }

Error Handling

Configuration access includes comprehensive error handling for undefined properties and invalid access patterns.

/**
 * Configuration errors thrown by get() method
 */
class ConfigError extends Error {
  message: string; // Description of the configuration error
}

// Error conditions:
// - get(null) or get(undefined) throws: "Calling config.get with null or undefined argument"
// - get('nonexistent.property') throws: 'Configuration property "nonexistent.property" is not defined'

Usage Examples:

const config = require('config');

// Error handling patterns
try {
  const value = config.get('missing.property');
} catch (error) {
  if (error.message.includes('is not defined')) {
    console.log('Property not found, using default');
    const value = 'default-value';
  }
}

// Safe access with has() check
function getConfigSafely(property, defaultValue) {
  return config.has(property) ? config.get(property) : defaultValue;
}

const dbTimeout = getConfigSafely('database.timeout', 5000);

// Validate arguments before calling get()
function getConfigValue(property) {
  if (property == null) {
    throw new Error('Property path cannot be null or undefined');
  }
  return config.get(property);
}