@nodifier/loguru

A simple and flexible logging utility for Node.js, inspired by Python's loguru. Provides easy-to-use logging with support for multiple transports (console, file), custom formatting, log levels, and context.

Features

• Simple API for logging at different levels (info, warn, error, debug, fatal)
• Pluggable transports (console, file, custom)
• Customizable log formats (JSON, plain text, etc.)
• Context support via child loggers
• TypeScript support

Installation

npm install @nodifier/loguru

Basic Usage (Singleton Logger)

import { logger } from '@nodifier/loguru';

logger.info('Hello, world!');
logger.warn('This is a warning');
logger.error('Something went wrong', { error: new Error('Oops') });
logger.debug('Debugging info', { data: { foo: 'bar' } });

Creating a Custom Logger Instance

import { Logger, ConsoleTransport } from '@nodifier/loguru';

const logger = new Logger({
  level: 'DEBUG',
  serviceName: 'MyService',
  transports: [new ConsoleTransport()],
});

logger.info('Custom logger instance!');

Using File Transport

import { Logger, FileTransport } from '@nodifier/loguru';

const logger = new Logger({
  level: 'INFO',
  serviceName: 'FileService',
  transports: [
    new FileTransport({ path: './logs/app.log', maxSize: 1024 * 1024 }),
  ],
});

logger.info('This will be written to app.log');

Using JSON Formatting

import { Logger, ConsoleTransport, JsonFormatter } from '@nodifier/loguru';

const logger = new Logger({
  level: 'INFO',
  serviceName: 'JsonService',
  transports: [new ConsoleTransport()],
  // The formatter is used internally by transports, but you can customize output in your own transport
});

// To format manually:
import { JsonFormatter } from '@nodifier/loguru';
const formatter = new JsonFormatter();
const formatted = formatter.format({
  timestamp: new Date().toISOString(),
  level: 'INFO',
  service: 'JsonService',
  message: 'Log as JSON',
});
console.log(formatted);

Adding Context with Child Loggers

import { logger } from '@nodifier/loguru';

const userLogger = logger.child({ userId: '1234' });
userLogger.info('User-specific log');

API Reference

• Logger(config: LoggerConfig): Create a new logger instance.
  • config.level: Minimum log level (DEBUG, INFO, WARN, ERROR, FATAL)
  • config.serviceName: Name of the service/application
  • config.transports: Array of transports (e.g., ConsoleTransport, FileTransport)
  • config.defaultMeta: Default metadata to include with every log
  • config.customLevels: Custom log levels (optional)
• logger.info(message, meta?): Log an info message
• logger.warn(message, meta?): Log a warning
• logger.error(message, meta?): Log an error
• logger.debug(message, meta?): Log a debug message
• logger.fatal(message, meta?): Log a fatal error
• logger.child(meta): Create a child logger with additional context

Transports

• ConsoleTransport(level?): Log to the console (stdout)
• FileTransport({ path, maxSize? }, level?): Log to a file with optional rotation

Formatter

• JsonFormatter: Formats log entries as JSON strings

License

MIT