Node.js is a programming environment used to develop web applications. Using node.js, developers can run JavaScript code on the server rather than only on the web pages. Node.js is prominent in the coding world for its advanced capability, enabling developers to build scalable and compatible applications.

Node.js can lead to the development of an improved and responsive web application. Instead of waiting for Input and Output operations, Node.js allows the developers to call back the functions executed when the operations are finished. It is compatible with operating systems, including Windows, Linux, and Mac devices, enabling you to build excellent apps on any platform.

It has gained significant recognition in information technology and is widely used in small and large sectors, creating advanced apps. It has a very strong and active community that has contributed to the improving and growing Information technology sector.

In Node.js, logging is the common practice for recording information, monitoring behaviors, and debugging applications. A logger is a valuable tool or module to manage and assist login within Node.js applications. Loggers track the execution, capture errors, and monitor the application's behavior.

Who uses the Node.js logger?

Various organizations use Node.js logger to manage their operations and developers to build various types of applications. One of the prime advantages of Node.js is it allows the use of JavaScript on both the client and server side.

Here are some examples of those who use Node.js for their operation:

• Technology companies – many prominent tech companies and startups use the Node.js loggers in their stack. Companies like PayPal, Netflix, Uber, and eBay have used Node.js in their applications.
• Social media – to handle a large number of concurrent connections, social media platforms like Facebook and Twitter use the Node.js logging libraries.
• Online retail stores – online retail websites like Amazon, eBay, and Walmart have implemented Node.js logging libraries in their stack to improve the overall performance of their operation.
• Startups – many startups use Node.js loggers due to their advanced features, rapid development capability, ability to handle enormous traffic, and availability of the vast ecosystem of various libraries and modules.

Popular and Best Libraries for Node.js

Follow the below list of the popular and best libraries for Node.js:

Winston: 

Winston is a popular logging library of Node.js that provides a flexible flow of data and handles application logs in a customized manner. It supports various log levels, log transport, and various customizable log formats. Winston provides several log levels, including:

• Error – for logging errors and critical issues.
• Warn – for logging warnings and potential issues.
• Info – for informational messages.
• Verbose – for detailed and verbose messages.
• Debug – for debugging messages.
• Silly – for extremely detailed and less relevant messages.

Winston supports various transports, including Console, File, HTTP, and more. You can log into multiple transports simultaneously. You can customize Winston further by adding more transports, modifying the log format, defining custom log levels, and integrating it with external services or databases, as needed.

Bunyan 

Bunyan is a fast and structured logging library for Node.js that focuses on producing a machine's readable log data in a JSON format. It's designed for performance and ease of use in applications that generate high volumes of logs. Bunyan provides log levels similar to other logging libraries. Some common log levels are 'info,' 'warn,' 'error,' 'debug,' and 'trace.' You can specify which log levels to display or store.  

Indeed, Bunyan is highly customizable. You can configure it to log into different transports, including files, streams, and external services. You can also define custom serializers and add additional data to log records. Bunyan emphasizes structured logging, which means log messages are in a machine-readable JSON format. This makes it easy to process and analyze logs with tools like Elasticsearch and Logstash. For log rotation, you can use external utilities like log rotate if you're logging into files. 

Moreover, Bunyan itself doesn't handle log rotation directly. Bunyan is a good choice when you need a performant, structured logging library that produces machine-readable logs, especially in scenarios where log data needs to be processed and analyzed efficiently.

Pino

Pino is a fast and lightweight Node.js logging library focusing on high performance and minimal overhead. It produces structured log messages in a JSON format, making it suitable for apps that need to log a significant amount of data with low overhead. Pino provides log levels similar to other logging libraries, such as 'info,' 'warn,' 'error,' 'debug,' and 'trace.' You can specify which log levels to display or store.

Moreover, Pino also supports serializers to add additional data to log records. You can define custom serializers to format log messages according to your needs. For log rotation, you can use external utilities like log rotate if you're logging into files. Pino itself doesn't handle log rotation directly.

Pino supports child loggers, allowing you to create separate loggers that inherit the configuration of their parent logger. It can be useful when adding information to your logs without duplicating the logger configuration. Pino is an excellent choice when you need a performant and lightweight logging library for apps that generate many logs. Its structure based on JSON logs is suitable for easy integration with log analysis and monitoring tools.

Log4js

Log4js is a Node.js logging library that provides flexible and configurable logging capabilities, similar to the popular Apache Log4j library. It supports various log levels, different appenders (outputs), and layouts for formatting log messages.Log4js is a Node.js logging library that provides flexible and configurable logging capabilities, similar to the popular Apache Log4j library. It supports various log levels, different appenders (outputs), and layouts for formatting log messages.

Log4js allows you to configure various aspects of logging, including log layout, appender options, log level, and more. You can customize the layout of log messages by specifying a pattern layout. You can also define custom appenders and layouts to suit your application's specific requirements.Log4js supports log file rotation. You can configure the 'file' appender to rotate log files automatically based on size or time.

Moreover, Log4js supports the concept of child loggers, which allows you to create separate loggers that inherit the configuration of their parent logger. Child loggers are useful for adding information relevant to context to logs without duplicating the logger configuration.Log4js is a powerful logging library with a rich feature set, making it suitable for various types of Node.js apps, from small scripts to large-scale apps. Its flexibility and configurability allow you to tailor your logging setup to your needs.

Morgan

Morgan is a widely used logging middleware for Node.js, specifically designed for logging HTTP requests and responses in web apps built with Express.js. It simplifies generating logs for your HTTP requests, making tracking and analyzing incoming and outgoing requests easier. 

Morgan is particularly useful for debugging and monitoring HTTP requests in your Express.js web apps. It helps you keep track of incoming requests, response times, and the overall behavior of your apps during development and in production environments.

Morgan provides several predefined formats:

• 'combined' - the most comprehensive log format.
• 'common' - a more compact log format.
• 'dev' - a development-friendly format with color-coded response status.
• 'short' - a shorter log format.

You can choose the format that best suits your needs. Remember that Morgan is primarily for logging HTTP requests and responses, and it's not a general logging library for all types of application logs. For more comprehensive logging-in applications that are not web-based, you may want to use a library like Winston or Bunyan in addition to Morgan for HTTP request logging.

Bristol

Bristol is a logging library for Node.js that aims to provide flexibility and ease of use for logging in your apps. It offers a variety of features and options. Bristol provides log levels similar to other logging libraries, including 'error,' 'warn,' 'info,' 'verbose,' 'debug,' and 'silly.' You can set the minimum log level to display or store in the configuration.

Indeed, Bristol is highly customizable. You can configure various options, including log formats, log targets, log levels, and additional data for log records. You can also define custom formatters and targets and add additional context data to log entries. You can use external utilities like 'logrotate' for log rotation. Bristol itself doesn't handle log rotation directly.

Moreover, Bristol supports the concept of child loggers, allowing you to create separate loggers that inherit the configuration of their parent logger. Child loggers are useful for adding specific information about context to logs without duplicating the logger configuration. Bristol is a feature-rich logging library that provides great flexibility and configurability. It's suited for various Node.js apps, from small scripts to complex, multi-component apps.

Conclusion

Node.js loggers are essential for several reasons, as they play a crucial role in debugging and monitoring Node.js applications. It will assist the development team in root cause analysis, troubleshooting, error tracking and reporting, capacity planning, and error prevention. The best logger for Node.js depends on your specific use case, performance requirements, preferred log format, and familiarity with the library. 

Winston is popular for its versatility, while Bunyan excels in high-performance structured logging. Undoubtedly, Pino is great for minimal overhead, and Log4js is a good option if you're familiar with Log4j. And Bristol offers a high level of customization. Morgan is tailored for Express.js applications. Additionally, you may find that different libraries are suitable for different aspects of your apps, so it's not uncommon to use a combination of logging libraries in a larger project.