Logging is an essential feature of finding and fixing problems in applications. It helps us to grab crucial info related to the application, like errors, warnings, messages, etc.
By using logging libraries in Node.js, we can track the metrics and performance of your application to get crucial details like response times, request rates, and resource usage. It is also useful for audits and making sure you follow the rules. Logging libraries also helps to get all the deets on errors and exceptions in the code.
You can even set log levels, and choose formats like JSON or plain text, basically, the uses of logging libraries have no limits. In this article, we will see the top 7 Node.js libraries that you can make use of for getting all of the mentioned and more features.
What is Logging in Node.js?
Logging in programming is fundamentally a crucial part of debugging code. With a logger in place, developers understand how their code is behaving, and what output is a code spitting out. It saves developers hours of coding. Logging is a way developers learn what technology or even their application is doing. For instance, if there’s an error with connecting to the server, an error log at this point will help point out what is the error and where it is coming from.
The console.log() function in JavaScript is mainly used for logging data. Although the console methods are of so much importance, it has failed at many things in which other custom Node.js logging packages have succeeded at. They give you the ability to do more, interact better and provide advanced features that accelerate overall development.
Best 7 Node.js Logging Libraries
Apart from console.log(), which is a great in-built Node.js logging tool, there lies a good number of Node.js logging libraries to help you customize logging as per your programming needs.
Let us take a quick look at what popular Node.js logging packages are available out there in the wild.
1. Log4js
Log4js is one of the popular tools used for Node.js logging. Published recently on NPM, this package has gained immense popularity because of the amazing features it offers for Node.js logging. While we write this article, it has received a weekly download of 3,537,547.
Syntax:
You can install it using the below NPM command.
npm i log4js
Features of Log4js
- The console can log coloured information to stderr or stdout.
- The file appender creates a rolling log based on the file size or the date.
- A connect/express server log for logging.
- Configurable layouts and patterns for log messages.
- Different loglevel for different log categories.
You can click here to view the detailed documentation of log4js.
2. Winston
The next on the list is the Winston package for Node.js logging. This too was published in a recent year and is more popular than log4js with a weekly download of 10,733,542. It is designed to be a simple logger for Node.js applications. It works on a concept called ‘transports’ that refer to storage areas for logs. These transports can be configured at different logging levels.
Syntax:
You can install it using the below NPM command.
npm i winston
Features of Winston
- Make use of multiple transports.
- Log transports can be customized.
- Make use of profiling.
- Handle exceptions.
- Select from a range of predefined error levels.
- Make your own custom error levels
You can click here to view detailed documentation of Winston.
3. Bunyan
Bunyan is another popular logging library that logs in JSON format. It is a newer package than the above two Node.js logging libraries. Bunyan aims to provide more structured logs and chooses JSON as the format. It has currently received a weekly download of 1,460,983.
Syntax:
You can install it using the below NPM command.
npm i bunyan
Features of Bunyan
- Simple and elegant Node.js logging API.
- Log records can be sent to a stream, a file, or rotated in a log file using an extensible streams system.
- A Bunyan log filter and pretty-printing CLI for Bunyan logs.
- Add source location (file, line, function) for log calls using src:true.
- Logger instance specialization with log.child that is lightweight.
- With serializers, log objects will be rendered in a customized way.
- A DTrace-based snooping system for logs during runtime.
- The runtime environment support includes Node.js, Browserify, Webpack, and NW.js.
You can click here to view detailed documentation of Bunyan.
4. Morgan
Morgan is a Node.js logging library for Express applications. Usually overlooked, this library is quite popular and powerful among its competitors. Published 3 years ago, this Node.js logging is the oldest on the list. It has received a weekly download of 4,018,119. It can be used as an express middle in apps.
Syntax:
You can install it using the below NPM command.
npm i morgan
Features of Morgan
- Versatile request and response logger for Express apps.
- Runs as middleware.
- Simple to use.
- Custom formats.
- Split/dual logging.
You can click here to view detailed documentation of morgan.
5. Pino
Pino brands itself as a very low-overhead logger for Node.js applications. It is said to be 5x times faster than its competitors. It has a command-line interface that matches that of Bunyan. It is the fastest JSON logger. It receives 5,077,468 weekly downloads on NPM.
It comes with a good range of web development framework support:
- Pino with Fastify
- Pino with Express
- Pino with Hapi
- Pino with Restify
- Pino with Koa
- Pino with Node core HTTP
- Pino with Nest
Syntax:
You can install it using the below NPM command.
npm i pino
Please refer to the above links if you want to install a framework-specific package.
Features of Pino
- Formatting and pretty print.
- Lower overhead.
- Fastest JSON logger.
- Runs all log processes called transports in a worker thread as recommended for Node.js.
- Minimal resource usage.
You can click here to view detailed documentation of Pino.
6. Frontail
Frontail is a Node.js application that helps users stream logs in the browser. It comes power-packed with a UI and a ton of features. It was first published 11 years ago on NPM and currently has 597 weekly downloads at the time of writing this article.
Syntax:
You can install it using the below NPM command.
npm i frontail
Features of Frontail
- Rotation of logs (not on Windows).
- Marking logs that automatically scroll.
- Logs paused.
- Favicon’s amount of unread logs.
- Highlighting
- Look for (Tab to focus, Esc to clear)
- Filter from URL parameter set.
- Multiple file tailing and stdin.
You can click here to view detailed documentation of Frontail.
7. Tracer
Tracer calls itself the customizable and powerful logging library for Node.js. With Tracer, you can print simple logs, and coloured logs, and even set output levels. You can customize it by printing a timestamp, file name, line number, and even the call stack! The list is huge!
It was first published 11 years ago making it the oldest in the list of best Node.js logging libraries. It currently receives weekly downloads of 55,622.
Syntax:
You can install it using the below NPM command.
npm i tracer
Features of Tracer
- Log messages can be printed with a timestamp, file name, method name, line number, path, or call stack.
- User-defined logging levels are supported by a customized output format with micro-template and timestamp format.
- Provides filter functions, allowing you to print statements in full colour and font size (colour console).
You can click here to view detailed documentation of Tracer.
Conclusion
In this tutorial, we have seen some popular Node.js logging libraries that you can use for logging data while developing Node.js applications. Each of the libraries mentioned can be easily downloaded using NPM direct from your terminal, just you have to make sure that NPM should be installed on the system in which you are downloading the library.
Each library will easily complete the basic logging task, but each has some unique features that we have mentioned, you can look at them to choose the most suitable library for yourself, and then you can refer to its documentation on NPM official websites for in-depth knowledge, use cases, logging tips & best practices for logging. At last, we hope you have enjoyed reading the content.
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