@valian/function-logger

A smart logger wrapper for Firebase Functions that automatically switches between production and development logging modes.

Features

• 🔄 Automatic Mode Switching: Uses Firebase Functions logger in production and tslog with pretty formatting during development
• 🎨 Beautiful Console Output: Color-coded logs with timestamps and source file information in development
• ⚙️ Configurable Log Levels: Control verbosity via environment variables
• 🔌 Drop-in Replacement: Compatible API with standard logging interfaces

Installation

npm install @valian/function-logger

Or with pnpm:

pnpm add @valian/function-logger

Usage

Basic Usage

import { logger } from '@valian/function-logger'

// Log at different levels
logger.debug('Debugging information')
logger.info('General information')
logger.warn('Warning message')
logger.error('Error occurred', error)

// Log multiple arguments
logger.info('User action:', { userId: '123', action: 'login' })

In Firebase Functions

import { onRequest } from 'firebase-functions/v2/https'
import { logger } from '@valian/function-logger'

export const myFunction = onRequest((request, response) => {
  logger.info('Function invoked', { path: request.path })

  try {
    // Your function logic
    logger.debug('Processing request...')
    response.send('Success')
  } catch (error) {
    logger.error('Function failed', error)
    response.status(500).send('Error')
  }
})

Configuration

Log Levels

Control the minimum log level by setting the LOG_LEVEL environment variable:

# Available levels (in order of verbosity)
LOG_LEVEL=debug  # Shows debug, info, warn, error (default)
LOG_LEVEL=info   # Shows info, warn, error
LOG_LEVEL=warn   # Shows warn, error
LOG_LEVEL=error  # Shows only error

Environment Detection

The logger automatically detects the environment:

• Development Mode: Uses tslog with pretty formatting when:

  • FUNCTIONS_EMULATOR=true (Firebase Emulator)
  • NODE_ENV=test (Testing environment)

• Production Mode: Uses Firebase Functions logger when running in deployed functions

API Reference

logger.debug(...args: any[])

Logs debug-level messages. Useful for detailed diagnostic information.

logger.log(...args: any[])

Alias for general logging (same as info).

logger.info(...args: any[])

Logs informational messages about normal application flow.

logger.warn(...args: any[])

Logs warning messages for potentially problematic situations.

logger.error(...args: any[])

Logs error messages for serious problems.

Development

This library is part of the firebase-functions monorepo.

Running Unit Tests

nx test logger

Or using pnpm:

pnpm nx test logger

License

MIT © Valian