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loglevelnext is a modern logging library for Node.js and modern browsers, written with modern patterns and practices which provides log level mapping of the console object.

Getting Started

First thing's first, install the module:

npm install loglevelnext --save


Users can choose to use loglevelnext in Node.js or in the client (browser).

// Node.js
const log = require('loglevelnext');

<!-- browser -->
    <script src="/path/to/loglevelnext.js"></script>

Log Levels

By default loglevelnext ships supporting the following log level name-value pairs:

  TRACE: 0,
  DEBUG: 1,
  INFO: 2,
  WARN: 3,
  ERROR: 4,

Default Logger

When requiring loglevelnext in Node.js the default export will be an instance of LogLevel wrapped with some extra sugar.

When loading the loglevelnext.js script in the client (browser), the script will assign window.log to an instance of LogLevel, wrapped with that same extra sugar.


Please see LogLevel for documentation of all methods and properties of every log instance, including the default instance.

trace, debug, info, warn, error

These methods correspond to the available log levels and accept parameters identical to their console counterparts. eg.

// ... etc


Returns a new LogLevel instance. The options parameter should be an Object matching the options for the LogLevel constructor.

Note: the logger returned is cached, and subsequent requests for a logger of the same name will return the same logger instance. If you require multiple unique loggers of the same name, pass an id property with a unique identifier and getLogger will use that over the name.


When using loglevelnext in a browser environment, you may encounter a scenario in which window.log is already assigned when the script loads, resulting in window.log being reassigned to loglevelnext. This method will restore window.log to it's original value and return the default logger.



Type: Array [ Class ]

Gets an Array containing the factory classes available within loglevelnext to outside modules. Particularily useful when creating plugins. eg.

const log = require('loglevelnext');
const { MethodFactory } = log.factories;
class MyFactory extends MethodFactory { ... }


Type: Array [ LogLevel ]

Gets an Array containing references to the currently instantiated loggers.

Factories aka Plugins

If you're used to using plugins with loglevel, fear not. The same capabilities are available in loglevelnext, but in a much more straightforward and structured way. loglevelnext supports by way of "Factories." A Factory is nothing more than a class which defines several base methods that operate on the console and provide functionality to a LogLevel instance. All factories must inherit from the MethodFactory class, and may override any defined class functions.

For an example factory, please have a look at the PrefixFactory which provides similar functionality as the loglevel-prefix plugin, and is the factory which is used when a user passes the prefix option to a LogLevel instance.

Persisting the Level

Persisting the level of a log between sessions in a browser isn't the job of a logging library. Primarily because working with localStorage these days is a breeze. If you need to store and retrieve a log level value between sessions, please look into leveraging the excellent and very tiny store2 library.

Browser Support

As mentioned, loglevelnext is a logging library for Node.js and modern browsers, which means the latest versions of the major browsers. Unfortunately "oldIE" versions aren't officially supported. The minimum Internet Exploder version supported is IE10, though Microsoft no longer supports it.

If you're in need of support for old or outdated browser versions, please use the older loglevel, which supports browsers as old as IE6.

Note: This library's distribution file is compiled in a way that will technically work all the way back to IE8 - as that version and above support localStorage. However, IE8 and IE9 require that the developer tools be open prior to invoking this library.


We welcome your contributions! Please have a read of CONTRIBUTING.md for more information on how to get involved.


This project is a fork of the much-loved loglevel module.

Base Log SVG by Freepik from www.flaticon.com.








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