Skip to content
Go to file

Latest commit

Fixing an issue with the way you configure an appender.

Git stats


Failed to load latest commit information.
Latest commit message
Commit time


Lightweight logging for JavaScript

Now with AngularJS support!

What is this?

Why would anyone want another logging framework for JavaScript? What's the point when there are perfectly good solutions such as Log4JS and Log4Javascript? Well, that's always a complicated answer, but my reasons were these:

The two projects mentioned are trying to emulate log4j for the Java platform. Who needs all that functionality when all that I really want to do is log messages? If you need something which carries a lot of weight, or has tons of features, go grab one of those projects. However, if you want something super lightweight, that doesn't require any third party libraries, then LogJS is probably for you.

Ok, so convince me!

LogJS is 4k uncompressed and less than 1k compressed and minified. It doesn't require jQuery or any other third party libraries. It comes with four simple appenders which can be used together or standalone. It's easy to write new appenders. It's not carrying around baggage to make it compatible with old browsers from days gone by. It has a set of tests to make sure it keeps on working.

What's an Appender?

LogJS can't do any logging itself - it needs an appender to do that. Essentially, an appender is the connection between the logger and the location for log messages to be sent. LogJS comes with a console appender to utilize the browser console, a DOM appender which will create a window to show log messages, a local storage appender which saves messages to a persistent store, and finally a CORS (Cross-Origin Resource Sharing) appender which can send messages to a server for storage.

It is possible to run as many appenders, or as few as you want. It's also possible to run without any appenders so that no logging is performed. This way, the logging can be left in the code without violating JSLint rules such as 'console.log'.

Enough already... How do I use this?

Simple. Add the following to your <head> section:

<script type='text/javascript' src='log.js'></script>

Then, put one of the logging calls into your scripts:

var x = 10;'The value of x is ' + x);

That's it!

Wait a second, I didn't see anything!

Right. This is where the Appenders come into play. After your script for LogJS, add the following and re-issue the logging statement:

<script type='text/javascript' src='appenders/console.js'></script>

Now you will see a log message in the console. Try loading another appender, such as the DOM appender, and you'll get a nifty in-page logging pane. This is where Appenders come in really handy! You can add as many, or as few, appenders as you want or need.

Configuration of Appenders

Some appenders require some configuration options to run, such as the LocalStorageAppender. You can set the interval between serializations and the maximum size of the buffer to maintain. It's important to note that the configuration for the appender is undefined, but should be passed as an object like below. For example:

<script type='text/javascript' src='log.js'></script>
<script type='text/javascript'>
   LogJS.config.LocalStorageAppender = {
      maxSize: 1 * 1024 * 1024  // 1 megabyte
<script type='text/javascript' src='appenders/localstorage.js'></script>


Due to the use of Object.defineProperty() and, this library doesn't work with IE8, Firefox 3.5 or 3.6, or Opera 10.5-11.5. All other browsers should work just fine. It has been officially tested with Chrome 23+ for OSX, Firefox 19+ for OSX, and Safari 6+ for OSX.

Using with AngularJS

The only requirement is to load AngularJS before you load LogJS and appenders. See /test/angular/index.html for a quick and dirty example of AngularJS integration.

Questions or Comments?

You can contact me at


Lightweight logging for JavaScript... now with AngularJS support!




No releases published
You can’t perform that action at this time.