TypeScript Logging library for both TypeScript and JavaScript
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TypeScript library for logging. Simple and flexible in usage.

  • The library is written in TypeScript, so it will easily integrate with other TypeScript projects.
  • Two styles are supported (either can be used or both):
    • Category style of logging
    • Log4j style of logging
  • Can run in both the browser and node
  • Api to control (console) logging at runtime through a (browser's) developer console.
  • Supports a separate chrome browser developer extension, which allows you to control logging at runtime through the chrome developer extension. For details please see: Typescript Logging Developer Extension

The javascript bundle can be used for normal javascript projects if needed (es5 compatible).

The following documentation sections are available:


  • Release 0.6.0 removed several previously deprecated methods e.a, please see the changelog to find out what
  • Build in combination with angular-cli 6.0.0+ may fail, for a workaround see Issue 36, until angular-cli fixes its regression.


Use npm to install for usage in your project.

npm install --save typescript-logging

No additional typings are required, these are included.

Requires typescript 2.4.2+ (tested).

Or download the (minified) javascript bundle and documentation from here.


The library does NOT ship with a polyfill of Promise anymore, this was done on purpose as shipping with a polyfill often lead to conflicts if other projects already have a different promise polyfill included.

So if you do care about old browsers, that do not have Promise support you must provide one yourself such as e.g. es6-promise.


The library provides two mechanisms for logging, one which looks similar to the widely known log4j like loggers and a new more experimental way of logging.

Which one to use, is a matter of preference, both have advantages and disadvantages.

Note: Currently the chrome developer extension supports "category style logging" only.

Category style logging

This provides a quick example, please check the documentation section for full documentation.


import {Category,CategoryLogger,CategoryServiceFactory,CategoryConfiguration,LogLevel} from "typescript-logging";

// Optionally change default settings, in this example set default logging to Info.
// Without changing configuration, categories will log to Error.
CategoryServiceFactory.setDefaultConfiguration(new CategoryConfiguration(LogLevel.Info));

// Create categories, they will autoregister themselves, one category without parent (root) and a child category.
export const catService = new Category("service");
export const catProd = new Category("product", catService);

// Optionally get a logger for a category, since 0.5.0 this is not necessary anymore, you can use the category itself to log.
  // export const log: CategoryLogger = CategoryServiceFactory.getLogger(cat);


import {catService,catProd} from "./Config"

export class ElseWhere {

  magic(name: string): void {
     // Normal log to category: catProd
     catProd.info("Performing magic: " + name);

     // Lambda log to catProd (cheaper)
     catProd.info(() => "Performing magic once more: " + name);

     catService.info(() => `With template script: ${name}`);

With the above example if magic("spell") is executed it will log:

2016-01-07 11:14:26,273 INFO [product] Performing magic: spell
2016-01-07 11:14:26,274 INFO [product] Performing magic once more: spell
2016-01-07 11:14:26,275 INFO [service] With template script: spell

Log4j style logging

This provides a quick example, please check the documentation section for full documentation.


import {LoggerFactory, LoggerFactoryOptions, LFService, LogGroupRule, LogLevel} from "typescript-logging";

// Create options instance and specify 2 LogGroupRules:
// * One for any logger with a name starting with model, to log on debug
// * The second one for anything else to log on info
const options = new LoggerFactoryOptions()
.addLogGroupRule(new LogGroupRule(new RegExp("model.+"), LogLevel.Debug))
.addLogGroupRule(new LogGroupRule(new RegExp(".+"), LogLevel.Info));

// Create a named loggerfactory and pass in the options and export the factory.
// Named is since version 0.2.+ (it's recommended for future usage)
export const factory = LFService.createNamedLoggerFactory("LoggerFactory", options);


import {factory} from "./ConfigLog4j";

// Retrieve a logger (you can decide to use it per class and/or module or just
// export it in the config above etc. Your loggers - your choice!).
// This logger will fall in the first LogGroupRule from above.
const log = factory.getLogger("model.Product");

// This logger will fall in the 2nd LogGroupRule
const logOther = factory.getLogger("somethingElse");

export class ElseWhere {

  magic(name: string): void {
    log.debug("Casting debug magic spell: " + name);
    logOther.info("Casting info magic spell: " + name);

    // Lamda logging, cheaper as its only executed when needed.
    log.debug(() => "Casting lambda debug magic spell: " + name);
    logOther.info(() => "Casting lambda info magic spell: " + name);

    // Use template script
    log.info(() => `Casting magic spell: ${name}`);

When the method magic("Lumina") is called on an ElseWhere instance, it will log:

2017-02-15 20:43:52,807 DEBUG [model.Product] Casting debug magic spell: Lumina
2017-02-15 20:43:52,809 INFO [somethingElse] Casting info magic spell: Lumina
2017-02-15 20:43:52,810 DEBUG [model.Product] Casting lambda debug magic spell: Lumina
2017-02-15 20:43:52,811 INFO [somethingElse] Casting lambda info magic spell: Lumina
2017-02-15 20:43:52,812 INFO [model.Product] Casting magic spell: Lumina

Console control API

The framework ships with an API that can be used to control the log settings dynamically, for both the log4j style and category styles of logging. This allows you to change log levels dynamically when an app is e.g. in production already.

For details how to use this, please read the console control documentation.

Exposing console control API when using webpack

When using webpack to bundle typescript-logging along, you need to expose it yourself, as webpack bundles the module inside making 'TSL' unavailable. Please read the documentation on page: Console control documentation for all details how to do this.


Download all documentation offline including API documentation of classes in addition to the normal documentation provided here.

Since version 0.2.0 the documentation has been split off in several sections.

Api and related

Webpack with more than one project module (important)

Note: This section is only relevant if you have multiple projects depending on each other and all need to use typescript-logging.


Whenever you use multiple projects, that are packed separately by webpack (thus each results in a separate bundle). You need to make sure to only have typescript-logging packed once in the final module. Not doing so will result in undesired unclear behavior. This is since the framework keeps state, and you only want it packed once because of that or state will be spread over different modules.


Project A is a core project (and thus used by other projects as a dependency), this project must make sure to not pack typescript-logging within it's module by using the external option:

var webpack = require("webpack");

module.exports = {
    ... more webpack config here

    externals : {
      "typescript-logging": "typescript-logging"


Then project B, that depends on project A should pack typescript-logging along normally (which is what webpack normally does if it's a dependency in package.json).

Typescript Logging Developer Extension

Starting with version 0.2.0+ a chrome developer extension is available to easily allow changing log levels and filtering of logging for an application that uses typescript logging.

Extension screenshot

Please visit: typescript-logging-extension on how to get this.

Note: The extension currently only integrates with the category style of logging.


To build locally:

npm run build


To run the tests:

npm run test


We all wish there were none in our software, but alas. If you encounter a bug please log it in the issue tracker.


Feel free to contribute or come up with great ideas, please use the issue tracker for that.

If you add/change new functionality and want it merged to master, please open a pull request. Also add tests for it (spec directory).

Some things may not fit the library and could be rejected, so if you are unsure please ask first before wasting your valuable time!

History and changelog

For history, changes and migration please check the changelog