clarity

A modern debug client for TypeScript, offering powerful logging capabilities with colored output, performance tracking, log rotation, and both CLI & library support.

Features

• 🚀 Performance High-Performance Logging
• 🎯 Domain-Specific Domain-Specific Namespaces
• 🤞 Buffering Fingers-Crossed Log Buffering
• 🔄 Rotation Automatic Log Rotation & Cleanup
• 🔐 Encryption Encrypted Log Storage

Output & Formatting

• 🎨 Rich Color-Coded Console Output
• 📊 Multiple Log Levels debug, info, success, warn, error
• 🔠 Format String Support %s, %d, %j, etc.
• ⚡ Built-in Performance Tracking start, end, time

Platform Support

• 🌐 Universal Browser & Server support
• 🛠️ CLI & Library Access APIs via CLI or programmatically
• 💻 Fully Typed First-Class TypeScript support
• 📦 Lightweight Zero external dependencies

Install

bun install clarity
npm install clarity

Get Started

There are two ways of using clarity: as a library or as a CLI.

Library

Given the npm package is installed:

import { Logger } from 'clarity'

// Configure the logger
const logger = new Logger('parser', {
  // Optional configuration
  maxLogSize: 5 * 1024 * 1024, // 5MB

  rotation: {
    maxLogFiles: 10,
    compress: true,
  },

  encrypted: true,
})

// Basic logging
logger.info('Starting parser...')
logger.success('Document parsed successfully')
logger.warning('Legacy format detected')
logger.error('Failed to parse document')

// Performance tracking
const end = logger.info('Starting expensive operation...')
// ... do work ...
end('Operation completed') // automatically includes time taken

// Domain-specific logging
const parseLogger = logger.extend('json')
parseLogger.info('Parsing JSON...') // outputs with [parser:json] prefix

// Debug mode
logger.debug('Additional debug information')

// Format string support
logger.info('Found %d errors in %s', 3, 'document.txt')

// Conditional execution
logger.only(() => {
  // Only runs when logging is enabled
  logger.info('Additional diagnostics...')
})

To learn more about the Library usage, please refer to the Library documentation.

Common Usage Examples

Basic Logging with Different Levels

import { Logger } from 'clarity'

const logger = new Logger('app')

// Different log levels
await logger.debug('Debug information for developers')
await logger.info('General information about application state')
await logger.success('Operation completed successfully')
await logger.warn('Warning: approaching rate limit')
await logger.error('Failed to connect to database')

Performance Tracking

import { Logger } from 'clarity'

const logger = new Logger('performance')

// Track operation duration
const end = logger.time('Starting database query')
await db.query('SELECT * FROM users')
await end() // Outputs: "Starting database query completed in 123ms"

// Track multiple operations
const end1 = logger.time('Operation 1')
const end2 = logger.time('Operation 2')
await Promise.all([
  someAsyncOperation().then(end1),
  anotherAsyncOperation().then(end2)
])

Domain-Specific Logging

import { Logger } from 'clarity'

const logger = new Logger('api')

// Create sub-loggers for specific domains
const authLogger = logger.extend('auth')
const dbLogger = logger.extend('database')
const cacheLogger = logger.extend('cache')

await authLogger.info('User authenticated') // [api:auth] User authenticated
await dbLogger.error('Connection failed') // [api:database] Connection failed
await cacheLogger.debug('Cache miss') // [api:cache] Cache miss

Advanced Configuration

import { Logger } from 'clarity'

const logger = new Logger('app', {
  // Log level and format
  level: 'debug',
  format: 'json',
  timestamp: new Date(),

  // Log rotation settings
  rotation: {
    maxSize: 5 * 1024 * 1024, // 5MB
    maxFiles: 10,
    frequency: 'daily',
    compress: true,
  },

  // Fingers-crossed buffering
  fingersCrossed: {
    activationLevel: 'error',
    bufferSize: 50,
    flushOnDeactivation: true,
  }
})

Structured Logging

import { Logger } from 'clarity'

const logger = new Logger('api', { format: 'json' })

// Log structured data
await logger.info('User action', {
  userId: 123,
  action: 'login',
  timestamp: new Date(),
  metadata: {
    ip: '192.168.1.1',
    userAgent: 'Mozilla/5.0...'
  }
})

// Log errors with stack traces
try {
  throw new Error('Database connection failed')
}
catch (error) {
  await logger.error('Failed to execute query', {
    error: error.message,
    stack: error.stack,
    query: 'SELECT * FROM users'
  })
}

Conditional Logging

import { Logger } from 'clarity'

const logger = new Logger('app')

// Only execute logging code if the level is enabled
logger.only(() => {
  const expensiveOperation = calculateSomething()
  logger.debug('Operation result:', expensiveOperation)
})

// Conditional logging with levels
if (logger.shouldLog('debug')) {
  const metrics = gatherMetrics() // expensive operation
  await logger.debug('System metrics:', metrics)
}

CLI

# Watch logs in real-time
clarity watch --level debug --name "parser:*"
clarity watch --json --timestamp

# Log a one-off message
clarity log "Starting deployment" --level info --name "deploy"

# Export logs to a file
clarity export --format json --output logs.json --level error
clarity export --start 2024-01-01 --end 2024-01-31

# Show and follow last N lines
clarity tail --lines 50 --level error --follow
clarity tail --name "api:*"

# Search through logs
clarity search "error connecting to database" --level error
clarity search "deployment" --start 2024-01-01 --case-sensitive

# Clear log history
clarity clear --level debug --before 2024-01-01
clarity clear --name "temp:*"

# Configure log rotation
clarity config set --key maxLogSize --value 5242880  # 5MB
clarity config set --key maxLogFiles --value 10
clarity config set --key compressLogs --value true

# Other configuration
clarity config set --level debug
clarity config list

# Utility commands
clarity --help    # Show help information
clarity --version # Show version number

All commands support the following common options:

• --level: Filter by log level (debug, info, warning, error)
• --name: Filter by logger name (supports patterns like "parser:*")
• --verbose: Enable verbose output

Command Reference

• watch: Monitor logs in real-time with filtering and formatting options
• log: Send one-off log messages with specified level and name
• export: Save logs to a file in various formats with date range filtering
• tail: Show and optionally follow the last N lines of logs
• search: Search through logs using patterns with date range and case sensitivity options
• clear: Clear log history with level, name, and date filtering
• config: Manage clarity configuration (get, set, list)

To learn more about the CLI usage, please refer to the CLI documentation.

Configuration

Clarity can be configured programmatically, using environment variables, or through the CLI:

Programmatic Configuration

import { Logger } from 'clarity'

const logger = new Logger('app', {
  // Log Levels
  level: 'debug',
  defaultName: 'app',
  verbose: true,

  // Output Format
  format: 'json',
  timestamp: true,
  colors: true,

  // Log Rotation
  rotation: {
    frequency: 'daily',
    maxLogSize: 10 * 1024 * 1024, // 10MB
    maxLogFiles: 5,
    compress: true,
  },

  encrypt: true,
  logDirectory: '~/.clarity/logs',
})

Environment Variables

# Enable logging
DEBUG=true
DEBUG=parser # enable specific logger
DEBUG=parser:* # enable logger and all subdomains

# Control log level
LOG_LEVEL=debug # show all logs
LOG_LEVEL=error # show only errors

CLI Configuration

# Configure logging
clarity config set --key level --value debug
clarity config set --key maxLogSize --value 5242880 # 5MB

Testing

bun test

Changelog

Please see our releases page for more information on what has changed recently.

Contributing

Please see CONTRIBUTING for details.

Community

For help, discussion about best practices, or any other conversation that would benefit from being searchable:

Discussions on GitHub

For casual chit-chat with others using this package:

Join the Stacks Discord Server

Postcardware

“Software that is free, but hopes for a postcard.” We love receiving postcards from around the world showing where clarity is being used! We showcase them on our website too.

Our address: Stacks.js, 12665 Village Ln #2306, Playa Vista, CA 90094, United States 🌎

Sponsors

We would like to extend our thanks to the following sponsors for funding Stacks development. If you are interested in becoming a sponsor, please reach out to us.

• JetBrains
• The Solana Foundation

Credits

• debug
• @open-draft/logger
• Chris Breuer
• All Contributors

License

The MIT License (MIT). Please see LICENSE for more information.

Made with 💙