Configuration and Customization

It's great and amazing that TogetherJS works so well, immediately upon installing it. However, there also are ways you can configure TogetherJS, so it'll reflect your needs. Because of the way TogetherJS is loaded, it's recommended that you make these configuration settings before TogetherJS has been loaded. For example:

    var TogetherJSConfig_siteName = "Reuven's page";
<script src="">

All of the configuration variables begin with TogetherJSConfig_ and have names that are fairly descriptive. A full list is on the TogetherJS site at, but you also can look through the together.js code, which contains comments describing what the configuration variables do.

For example, if you decide you want to run your own hub (that is, a message-passing, WebSockets-based server), you must tell TogetherJS to look in a different location, with TogetherJSConfig_hubBase.

Other useful configuration variables are:

  • TogetherJSConfig_useMinimizedCode: downloads the minimized JavaScript files for the rest of TogetherJS.

  • TogetherJSConfig_inviteFromRoom: allows you to think about collaboration on a site-wide basis.

  • TogetherJSConfig_youtube: when set, this means that if one person views a YouTube video, everyone will, and they will be synchronized.

But, TogetherJS provides more than just the ability to configure and use it. You also can extend it. The same message-passing system that TogetherJS uses for itself is available to developers. Thus, you can send arbitrary messages, for arbitrary events, between all of the people currently collaborating on this system.

In order to send an arbitrary JSON message, all of the parties involved need to agree on the message "type"—that is, the string that you will use to identify your message. All parties also need to register their interest in receiving messages of this type and to define a callback function that will fire when the message is sent. Although it makes sense to do this within the HTML or JavaScript in your application, it's also possible to do it in your favorite browser's JavaScript console.

First, you register interest in your object by telling TogetherJS that whenever it receives a message of a certain type from a hub (using the TogetherJS.hub.on methods), it should fire a particular callback:

        function (msg) {
            console.log("message received: " + msg)

Now, it's true that because your message is an object, it will be printed as "[Object object]" in the Web console, which is really too bad. If you prefer, you can choose individual fields from the object, but be sure that you know what fields you will be receiving.

To send a message, just invoke TogetherJS.send along with a JSON object that will be sent to all of the other TogetherJS subscribers on this channel. There is no way to send a message to one particular computer; in this way, the paradigm is similar to what you probably saw with real-time Web updates with Pusher and PubNub last year.

To send a message, you use the following:

TogetherJS.send({type: "reuvenTest", foo: 
 ↪'foofoo', bar: 'barbar'});

I should note that both of these methods return undefined to the caller. Normally, this isn't a problem, but if you're working in the console, you might not expect such a response.

Of course, the power of this communication channel is in deciding what you want to communicate, and what should happen when communication comes in. When a message arrives, do you want to change the way something is displayed on the receivers' screens? Do you want to display a message for the user?


TogetherJS is relatively new, and I am still in the early stages of using it in my applications that require real-time collaboration. That said, TogetherJS is an interesting application in and of itself, and it was designed as a platform that will continue to grow and expand. With TogetherJS, we are one additional step closer to using the Web for new and different forms of collaboration.


The home page for TogetherJS is, but the GitHub page is You can use TogetherJS with any modern browser, which basically means that it does not support Internet Explorer. I was able to get it to work with Firefox, Chrome and Safari (on OS X) without any problems. Note: TogetherJS explicitly states that it doesn't support Internet Explorer very well, including the most recent versions, which means that if you're working in a mixed environment, it might not be a good choice.


Reuven M. Lerner, Linux Journal Senior Columnist, a longtime Web developer, consultant and trainer, is completing his PhD in learning sciences at Northwestern University.

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