Logger

A simple and efficient logging system that saves records in CSV format with timestamps and severity levels.

Description

Logger is a Node.js application that provides a lightweight and functional logging system. It records messages with different severity levels (INFO, WARN, ERROR, DEBUG) in CSV files organized by date.

Features

• ✅ Logging with multiple levels (INFO, WARN, ERROR, DEBUG)
• ✅ CSV files organized by date
• ✅ Timestamps in ISO 8601 format
• ✅ Support for additional metadata
• ✅ Automatic directory handling
• ✅ Robust CSV format with special character escaping
• ✅ NEW v2.0.0: Colored console output with Chalk library
• ✅ NEW v2.0.0: Real-time console logging while writing to CSV files
• ✅ NEW v2.0.0: Color-coded log levels (blue for INFO, gray for DEBUG, yellow for WARNING, red for ERROR)
• ✅ NEW v2.1.0: Caller information tracking (file name and line number)

Installation

Prerequisites

• Node.js 12 or higher
• npm (included with Node.js)

Steps

1. Clone or download this repository:

git clone <repository-url>
cd logger

2. Install dependencies (if any):

npm install

OR

npm install git+https://github.com/rusker86/logger.git

Dependencies

The project uses the following dependencies:

• chalk: ^5.6.2 - For colored terminal output

Testing

The project includes a comprehensive test suite using Node.js built-in testing framework.

Running Tests

Run all tests:

npm test

Run tests with verbose output:

npm run test:verbose

Test Coverage

The test suite includes 79 tests covering:

• ✅ Date utilities (getTodayDate, getTimeStamp)
• ✅ CSV formatting (toCSVRow)
• ✅ Caller information extraction (getCallerInfo)
• ✅ Console logging with colors
• ✅ File stream writing (NEW)
• ✅ Logger creation and initialization
• ✅ Optional caller information (NEW)
• ✅ All logging methods (info, warn, error, debug)
• ✅ File operations and organization
• ✅ Metadata handling
• ✅ Edge cases and error handling

See tests/README.md for detailed test documentation.

Project Structure

logger/
├── createLogger.js           # Logger factory function
├── index.js                  # Main entry point
├── package.json              # Project dependencies and configuration
└── utils/
    ├── csv.js                # CSV format utilities
    ├── date.js               # Date and timestamp handling utilities
    ├── logToConsole.js       # Console output with color formatting
    ├── callerInfo.js         # Caller information extraction
    └── writer.js             # File stream writer utilities

Usage

Starting the application

npm run start

Creating a logger instance

import { createLogger } from "./createLogger.js"

// Create logger with default options (callerInfo enabled)
const logger = createLogger()

// Create logger with custom directory
const logger = createLogger({ logDir: "./mylogs" })

// Create logger without caller information in messages
const logger = createLogger({ callerInfo: false })

// Combine options
const logger = createLogger({ 
	logDir: "./logs",
	callerInfo: true  // Default: includes file name and line number
})

Using the logger

// Log information
logger.info("Server started")

// Log warnings
logger.warn("Unusual condition detected", { userId: 123 })

// Log errors
logger.error("An error occurred", { code: 500 })

// Log debug information
logger.debug("Variable x = 42", { variable: 42 })

Method Signature

All logger methods accept a message and optional metadata:

logger.info(message: string, meta?: object)
logger.warn(message: string, meta?: object)
logger.error(message: string, meta?: object)
logger.debug(message: string, meta?: object)

Options

• logDir (string): Directory where log files will be saved. Defaults to "logs". Can be absolute or relative path.
• callerInfo (boolean): Include caller file name and line number in log messages. Defaults to true.

Log Format

Logs are saved in CSV files in the logs/ directory with the filename YYYY-MM-DD.csv.

Each line contains:

• Timestamp: Exact time in ISO 8601 format
• Level: [INFO], [WARN], [ERROR], or [DEBUG]
• Message: Descriptive text of the event
• Metadata: Additional data in JSON format (optional)

Example:

2026-01-22T15:30:45.123Z,[INFO],Server started,
2026-01-22T15:30:46.456Z,[WARN],Unusual condition detected,{"userId":123}
2026-01-22T15:30:47.789Z,[ERROR],An error occurred,{"code":500}

Console Output

Starting from v2.0.0, logs are displayed in the console with color coding for better visibility:

• 🔵 [INFO] - Blue
• 🟡 [WARNING] - Yellow
• 🔴 [ERROR] - Red
• ⚫ [DEBUG] - Gray

Example console output:

[INFO], Server started,
[WARNING], Unusual condition detected, {"userId":123}
[ERROR], An error occurred, {"code":500}

Logs are simultaneously written to CSV files and displayed in the console with real-time color formatting This project has no external dependencies. It uses only native Node.js modules.

Main Modules

utils/logToConsole.js

Utility for displaying logs in the terminal with color formatting using Chalk:

• Maps log levels to specific colors
• Automatically formats messages and metadata for console display
• Enhances log visibility with color-coded severity levels

createLogger.js / index.js

Central module that exports the logger object with four logging levels. It manages the creation of daily log files and record writing.

utils/csv.js

Utility for converting arrays of values to valid CSV format, with automatic handling of:

• Null or undefined values
• Objects (converted to JSON)
• Special characters (commas, quotes, line breaks)

utils/date.js

Functions to get:

• getTodayDate(): Current date in YYYY-MM-DD format
• getTimeStamp(): Timestamp actual en formato ISO 8601

utils/callerInfo.js

Extracts caller information from the call stack:

• getCallerInfo(): Returns an object with file and line properties
• Useful for debugging to identify the exact location where a log was called
• Returns {file: string, line: number}

utils/writer.js

Manages file stream writing for log files:

• createWriter(filePath): Creates a writer instance for appending to files
• write(line): Writes content to the file stream
• close(): Properly closes the file stream
• Uses append mode to preserve existing log entries
• Returns {write, close} object

Licencia

MIT