Loggerfy

A simple and structured logging library for Node.js applications

What is Loggerfy?

Loggerfy is a lightweight library that helps you create structured logs with a consistent format. Perfect for applications that need an organized and easy-to-implement logging system.

Quick Installation

1npm install loggerfy

Quick Start Guide

1. Import the library

1// CommonJS
2const { Loggerfy } = require('loggerfy');
3
4// ES Modules
5import { Loggerfy } from 'loggerfy';

2. Create a logger and use it

1// Create an instance
2const logger = new Loggerfy();
3
4// Log an error
5logger.error()
6  .setCode('AUTH_001')
7  .setMessage('User authentication failed')
8  .setDetail('Invalid credentials provided')
9  .setMetadata({ userId: 123 })
10  .write();

Log Levels

Loggerfy offers three logging levels:

1// Information
2logger.info()
3  .setCode('APP_001')
4  .setMessage('Application started')
5  .setDetail('Server listening on port 3000')
6  .write();
7
8// Warning
9logger.warn()
10  .setCode('CONFIG_001')
11  .setMessage('Using default configuration')
12  .setDetail('Configuration file not found')
13  .write();
14
15// Error
16logger.error()
17  .setCode('DB_001')
18  .setMessage('Database connection error')
19  .setDetail('Timeout after 30 seconds')
20  .write();

Available Methods

Method	Description	Required?
setCode(code)	Sets a unique code for the log entry	Yes
setMessage(message)	Sets the main message	Yes
setDetail(detail)	Adds additional details	Yes
setMetadata(object)	Adds contextual data	No
write()	Writes the log to the console	Yes*
getLog()	Returns the log as a JSON string without printing	Yes*

*Either write() or getLog() must be called to complete the logging operation.

Getting Log as String

If you need the log as a string instead of printing it to the console:

1// Get log as JSON string
2const logString = logger.error()
3  .setCode('AUTH_001')
4  .setMessage('User authentication failed')
5  .setDetail('Invalid credentials provided')
6  .setMetadata({ userId: 123 })
7  .getLog();
8
9// Now you can use the string however you want
10sendToExternalService(logString);

Output Format

All logs are generated in JSON format:

1{
2  "timestamp": "2023-11-15T14:30:45.123Z",
3  "id": "550e8400-e29b-41d4-a716-446655440000",
4  "code": "AUTH_001",
5  "message": "User authentication failed",
6  "detail": "Invalid credentials provided",
7  "payload": { "userId": 123 },
8  "level": "ERROR",
9  "severity": "ERROR",
10  "service": "my-service",
11  "environment": "development"
12}

Environment Customization

Loggerfy automatically detects the environment and service name:

1// Configure environment variables
2process.env.SERVICE_NAME = "user-api";
3process.env.NODE_ENV = "production";
4
5// Logs will include these values

Implementation with Custom Repository

You can save logs to a custom repository:

1import { Loggerfy, LoggerfyRepository, LogEntry } from 'loggerfy';
2
3// Implement your repository
4class MyRepository implements LoggerfyRepository {
5  async save(log: LogEntry): Promise<void> {
6    // Save the log to your database
7    await db.logs.insert(log);
8  }
9}
10
11// Create the logger with your repository
12const logger = new Loggerfy(new MyRepository());
13
14// Use it normally
15logger.info()
16  .setCode('USER_001')
17  .setMessage('User created')
18  .setDetail('New record in database')
19  .write();

Complete Example

1import { Loggerfy } from 'loggerfy';
2
3// Environment configuration
4process.env.SERVICE_NAME = "payment-service";
5
6const logger = new Loggerfy();
7
8function processPayment(userId, amount) {
9  try {
10    // Payment processing logic
11    
12    // Success log
13    logger.info()
14      .setCode('PAYMENT_001')
15      .setMessage('Payment processed successfully')
16      .setDetail(`Payment of $${amount} processed`)
17      .setMetadata({ userId, amount, timestamp: new Date() })
18      .write();
19      
20    return true;
21  } catch (error) {
22    // Error log
23    logger.error()
24      .setCode('PAYMENT_ERR_001')
25      .setMessage('Payment processing failed')
26      .setDetail(error.message)
27      .setMetadata({ userId, amount, errorStack: error.stack })
28      .write();
29      
30    return false;
31  }
32}

Tips for Effective Use

1. Use consistent codes - Create a coding system for your logs (e.g., AUTH_001, DB_001)
2. Include context - Use setMetadata to add relevant information for debugging
3. Use the appropriate level - Don't log everything as an error, use info and warn appropriately
4. Choose the right output method - Use write() for console output or getLog() when you need the log as a string

Need Help?

Visit our GitHub repository for more information or to report issues.