@lennardgeissler/logger

A flexible, extensible TypeScript logging library that works in both browser and Node.js environments. Supports multiple handlers, formatters, and log levels.

🚀 Features

• 🌟 Works in both browser and Node.js environments
• 🎨 Customizable formatters (Text, JSON)
• 📝 Multiple handlers (Console, File, Storage)
• 🔍 Log levels (debug, info, warn, error, fatal)
• 🎯 TypeScript support
• 🧪 Well tested
• 🔄 Singleton pattern for consistent logging
• 💾 Browser storage support (localStorage/sessionStorage)

🔧 Installation

npm install @lennardgeissler/logger

📖 Usage

import { Logger, ConsoleHandler, TextFormatter } from '@lennardgeissler/logger';
// Get logger instance
const logger = Logger.getInstance();
// Add handler with custom formatter
const handler = new ConsoleHandler();
handler.setFormatter(new TextFormatter('[{timestamp}] [{level}] {message}'));
logger.addHandler(handler);
// Start logging!
logger.info('Application started', { version: '1.0.1' });
logger.debug('Debug message');
logger.warn('Warning message', { details: 'Something went wrong' });
logger.error('Error occurred', { error: new Error('Failed to process') });

📝 Handlers

ConsoleHandler

Outputs logs to the console with color support in browsers.

import { ConsoleHandler } from '@lennardgeissler/logger';
const handler = new ConsoleHandler();
logger.addHandler(handler);

FileHandler

Outputs logs to a file (Node.js environment).

import { FileHandler } from '@lennardgeissler/logger';
const handler = new FileHandler('app.log');
logger.addHandler(handler);

StorageHandler

Stores logs in browser's localStorage or sessionStorage.

import { StorageHandler } from '@lennardgeissler/logger';
const handler = new StorageHandler(false, 'app-logs');
logger.addHandler(handler);

🎨 Formatters

TextFormatter

Formats logs as plain text using a customizable template.

import { TextFormatter } from '@lennardgeissler/logger';
const formatter = new TextFormatter('[{timestamp}] [{level}] {message}');
handler.setFormatter(formatter);

JSONFormatter

Formats logs as JSON strings.

import { JsonFormatter } from '@lennardgeissler/logger';
const formatter = new JsonFormatter();
handler.setFormatter(formatter);

📝 Log Levels

Available log levels in order of severity:

• debug
• info
• warn
• error
• fatal

Set minimum log level:

logger.setLevel('warn'); // Only warn, error, and fatal will be logged

🧰 Custom Handlers

Create custom handlers by extending BaseHandler:

import { BaseHandler, LogMessage } from '@lennardgeissler/logger';
class CustomHandler extends BaseHandler {
    handle(log: LogMessage): void {
    // Your custom logging logic here
    const formattedLog = this.formatter.format(log);
    // ... handle the formatted log
    }
}

🎨 Custom Formatters

Create custom formatters by extending BaseFormatter:

import { BaseFormatter, LogMessage } from '@lennardgeissler/logger';
class CustomFormatter extends BaseFormatter {
    format(log: LogMessage): string {
        // Your custom formatting logic here
        return `Custom format: ${log.message}`;
    }
}

📝 Changelog

See CHANGELOG.md for release history.

🤝 Contributing

Contributions are welcome! If you would like to contribute, please follow these steps:

1. Fork the repository.
2. Clone your fork to your local machine.
3. Create a new branch: git checkout -b feature/my-new-feature.
4. Make your changes and commit them: git commit -am 'Add new feature'.
5. Push your branch to your fork: git push origin feature/my-new-feature.
6. Open a pull request to merge your changes into the main repository.

📝 License

This project is licensed under the MIT License - see the LICENSE file for details.

👨‍💻 Authors

• Lennard Geissler (@LennardGeissler)