@midtownhi/logger

A NestJS-style configurable TypeScript logger with colored output and log levels.

Installation

npm install @midtownhi/logger

Features

• Multiple log levels: ERROR, WARN, LOG, DEBUG, VERBOSE
• NestJS-compatible API with both static and instance methods
• Colored output for better readability
• Contextual logging with global and per-instance contexts
• Timestamp support
• Environment-aware behavior with production safeguards
• Global log level control

Usage

Static Usage (NestJS-style)

import { Logger, LogLevel } from '@midtownhi/logger';

// Use static methods (similar to NestJS)
Logger.log('This is a regular log message');
Logger.error('Something went wrong!', 'Optional stack trace');
Logger.warn('This is a warning');
Logger.debug('Debug information');
Logger.verbose('Very detailed information');

// With context
Logger.log('Message with context', 'ContextName');

// Set global context for all static calls
Logger.setGlobalContext('AppName');
Logger.log('Will use AppName context');

Instance Usage

import { Logger, LogLevel } from '@midtownhi/logger';

// Create a logger with a context
const logger = new Logger('MyComponent');

// Log at different levels
logger.log('This is a regular log message');
logger.error('Something went wrong!', 'Optional stack trace');
logger.warn('This is a warning');
logger.debug('Debug information');
logger.verbose('Very detailed information');

// Change context at runtime
logger.setContext('NewContext');

// Create a contextual logger
const authLogger = Logger.getInstance('Auth');
const dbLogger = Logger.getInstance('Database');

Log Level Control

import { Logger, LogLevel } from '@midtownhi/logger';

// Set global log level (affects all loggers)
Logger.setLogLevel(LogLevel.WARN);

// Set per-instance log level (only works in development)
const logger = new Logger('MyComponent');
logger.setLogLevel(LogLevel.DEBUG);

// In production, all loggers use the global log level regardless of settings

Production Mode Behavior

In production (process.env.NODE_ENV === 'production'):

• The global log level defaults to LogLevel.LOG
• All logger instances use the global log level, regardless of instance settings
• Attempts to override log levels are ignored
• This ensures consistent, controlled logging in production environments

In development:

• The global log level defaults to LogLevel.DEBUG
• Logger instances can have custom log levels
• Per-call log level overrides work normally

Log Levels

• ERROR: Only critical errors
• WARN: Errors and warnings
• LOG: Errors, warnings, and regular logs (default in production)
• DEBUG: Everything above plus debug messages (default in development)
• VERBOSE: All messages, including the most detailed ones

API

Static Methods

• Logger.log(message, context?): Regular log messages
• Logger.error(message, trace?, context?): Error messages with optional stack trace
• Logger.warn(message, context?): Warning messages
• Logger.debug(message, context?): Debug information
• Logger.verbose(message, context?): Very detailed information
• Logger.getInstance(context?): Get or create a logger instance with context
• Logger.setLogLevel(level): Set the global log level for all loggers
• Logger.setGlobalContext(context): Set global context for static methods

Constructor

new Logger(context?, options?)

Creates a new logger instance.

• context (optional): A string context name to include in log messages
• options (optional): Configuration options object

Options

• timestamp (boolean): Whether to include timestamps (default: true)
• level (LogLevel): Instance log level (ignored in production)

Instance Methods

• log(message, context?): Regular log messages
• error(message, trace?, context?): Error messages, with optional stack trace
• warn(message, context?): Warning messages
• debug(message, context?): Debug information
• verbose(message, context?): Very detailed information
• setLogLevel(level): Change this instance's log level (no effect in production)
• setContext(context): Change this instance's context
• createLoggerWithContext(context): Create a new logger with specified context

Implementing Custom Loggers

The library exports a LoggerService interface that can be implemented for custom logging solutions:

export interface LoggerService {
    log(message: any, context?: string): void;
    error(message: any, trace?: string, context?: string): void;
    warn(message: any, context?: string): void;
    debug(message: any, context?: string): void;
    verbose(message: any, context?: string): void;
    setContext(context: string): void;
    setLogLevel(level: LogLevel): void;
}

License

MIT