Getting Started

Get up and running with @sylphx/cat in minutes.

Installation

npm

npm install @sylphx/cat

bun

bun add @sylphx/cat

pnpm

pnpm add @sylphx/cat

yarn

yarn add @sylphx/cat

Basic Usage

Create a logger and start logging:

import { createLogger } from '@sylphx/cat'

const logger = createLogger()

logger.info('Application started')
logger.warn('This is a warning')
logger.error('Something went wrong')

With Formatters and Transports

Configure how logs are formatted and where they go:

import {
  createLogger,
  prettyFormatter,
  consoleTransport,
  fileTransport
} from '@sylphx/cat'

const logger = createLogger({
  level: 'info',
  formatter: prettyFormatter({
    colors: true,
    timestamp: true
  }),
  transports: [
    consoleTransport(),
    fileTransport({ path: './logs/app.log' })
  ]
})

logger.info('Hello world!')

Structured Logging

Add structured data to your logs:

logger.info('User logged in', {
  userId: '123',
  action: 'login',
  ip: '192.168.1.1',
  timestamp: Date.now()
})

// Output (JSON format):
// {
//   "level": "info",
//   "msg": "User logged in",
//   "data": {
//     "userId": "123",
//     "action": "login",
//     "ip": "192.168.1.1",
//     "timestamp": 1234567890
//   }
// }

Child Loggers

Create child loggers with inherited context:

const logger = createLogger({
  context: {
    app: 'my-api',
    version: '1.0.0'
  }
})

// Create child logger for auth service
const authLogger = logger.child({
  service: 'auth'
})

authLogger.info('User authenticated', { userId: '123' })
// Includes: app, version, service, userId

Next Steps

• Core Concepts - Understand loggers, formatters, and transports
• Security - Learn about data redaction and OWASP compliance
• Observability - Integrate with OpenTelemetry
• Examples - Browse real-world examples

Quick Links

• API Reference - Complete API documentation
• Migration Guide - Migrate from Pino or Winston
• Best Practices - Production tips and patterns