Logging in TypeScript Applications: Best Practices for Beginners

Introduction to Logging in TypeScript Applications

Logging is the process of recording events that occur during program execution. For TypeScript applications, especially those running in a Node.js environment, properly configured logging is not just good practice, but a critically important tool for debugging, monitoring, and error analysis.

Many beginner developers limit themselves to using console.log(). However, in a production environment, this approach is ineffective: it does not allow you to flexibly manage severity levels, filter messages, or save them to files. In this article, we will look at how to create a professional logging system in TypeScript from scratch.

Why You Shouldn't Use console.log in Production?

Let's look at a typical example:

// Bad approach — using console.log directly\nfunction processOrder(orderId: string): void {\n  console.log(`Processing order ${orderId}`);\n  try {\n    // business logic\n  } catch (error) {\n    console.error(`Error processing order: ${error}`);\n  }\n}\n

Problems with this approach:

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• Lack of logging levels: you cannot separate debug messages from critical errors.
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• No formatting: difficult to read large amounts of data.
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• Cannot redirect: all messages go only to stdout/stderr.
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• Performance issues: synchronous console writing can slow down the application.
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Best Practices for Logging in TypeScript

1. Choosing a Logging Library

For TypeScript, it is recommended to use one of two popular libraries:

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• Winston — a powerful and flexible logger with support for transports (file, console, databases).
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• Pino — an ultra-fast logger, ideal for high-load applications.
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Let's install Winston:

npm install winston\nnpm install @types/winston --save-dev\n

2. Creating a Configurable Logger

Let's create a logger.ts module:

import winston from 'winston';\n\nconst logger = winston.createLogger({\n  level: process.env.LOG_LEVEL || 'info',\n  format: winston.format.combine(\n    winston.format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss' }),\n    winston.format.errors({ stack: true }),\n    winston.format.json()\n  ),\n  transports: [\n    new winston.transports.Console({\n      format: winston.format.combine(\n        winston.format.colorize(),\n        winston.format.simple()\n      )\n    }),\n    new winston.transports.File({ \n      filename: 'logs/error.log', \n      level: 'error' \n    }),\n    new winston.transports.File({ \n      filename: 'logs/combined.log' \n    })\n  ]\n});\n\nexport default logger;\n

Now you can use the logger in any module:

import logger from './logger';\n\nfunction getUser(id: string) {\n  logger.info(`Fetching user with ID: ${id}`);\n  try {\n    // user retrieval logic\n    logger.debug('User data retrieved successfully');\n  } catch (error) {\n    logger.error('Failed to fetch user', { userId: id, error });\n  }\n}\n

3. Using Logging Levels

Standard levels (from least to most important):

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• debug — detailed debugging information (development only).
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• info — standard informational messages.
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• warn — warnings about potential issues.
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• error — errors requiring attention.
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Configure the logging level via environment variables:

// In .env file\nLOG_LEVEL=debug  # for development\nLOG_LEVEL=warn   # for production\n

4. Structured Logging

Pass additional