An experiment in collaborative user experiences.

The chat.os server provides a small set of functionality to enable real-time communication and the ability to alter the environment via persisted client-side code. It should be capable of producing rich collaborative spaces, but the capabilities of any of these spaces will be determined by the level of effort invested by the participants.


Chat.os requires Node.js, npm, and MongoDB be installed. Currently MongoDB must run on its default port. After installing the chat.os project:

cd chat.os
npm install


Chat.os relies on Google accounts for authentication (more options coming soon). To create an instance of the server, you must create a google project using the project console. Next copy the config_example.js file in the root of the project to config.js and edit it. Choose a randomish string for the session secret and set the authentication parameters provided from the google project console. Once the configuration is in place, you're ready to run the server:

node server.js

Running Tests

Chat.os uses mocha.js to test server side functionality. To run the tests:



To begin, go to the home page on the server (i.e. http://localhost:8500/), click the link to log in through google accounts, and follow the instructions from there. Once you've been authenticated and authorized the application, you will land on the rooms page where you can create an existing room or create a new one. Once in a room, you will be chatting with everyone else currently in that room. If the room is new, there will only be a single text field at the top of page where you can enter comments and commands.


Typing anything into the input will create a comment that will be broadcast to others in the room. You may enter commands by prepending the first word with a colon like:

:move into the red room

In this case, the command type will be 'move' and it's body will be 'into the red room'. To send structured data, enter a JSON object literal after the type. For example:

:flash {delay:500, repeat:20, text:'boo'}

There are a few typed commands that will be important for upgrading a room, and room upgrades will provide addional commands to communicate and alter the space.

Special Commands


The upgrade command is probably the most important command. It allows you to inject HTML, CSS, and script into the room. It's syntax is:

:upgrade { name:[name], markup:[html], style:[css], script:[js] }

Where name is the name of the upgrade, markup is the HTML to inject, style is the CSS to inject, and script is the Javascript to inject. All three of these should be string escaped. When the upgrade is added to the page the application will do its best to replace and existing upgrade with the same name.

If the top level elements in the markup have an id, any existing elements matching that id will be removed before the new elements are added (so refreshing the upgrade won't append redundant markup). It's good practice to prepend the name of the upgrade to every id in the markup.

Any CSS for a previous upgrade with the same name will be replaced by the new upgrade. Thats true for the JS as well, but special care needs to be taken to avoid global effects that can't be undone.

Upgrades are tied to a room. All upgrades to a room will be added whenever anyone enters the room. Saving an upgrade will replace an existing upgrade with the same name and then broadcast the new version (there is currently no concept of versioning).


The import command pulls an upgrade from another room into the current room.

:import [room]::[upgrade]

Where room is the name of the room and upgrade is the name of the upgrade. The incoming upgrade will have the same name and will overwrite an upgrade with the same name in the current room.


Remove an upgrade.

:remove [upgrade]

Where upgrade is the name of the upgrade. Removed upgrades cannot be retrieved. Removing an upgrade forces a page refresh for everyone in the room.


Force a page refresh for all room participants



The replay command searches the current room for messages previously sent to the room and resends them only to the current user (i.e. the messages are not broadcast).

:replay { oftype:[type], since:[time], limit:[count] }

All of the search criteria are optional. Type may be a single string or an array of types.

Replay messages are useful to initialize upgrades after startup. For example, a poll upgrade may replay all vote messages to display the current tally after startup.


The rollcall command requests a list of all the room participants with active connections. A rollcall response will be sent that contains the identities of all people in the room.

:rollcall {}

responds with:

{type:'rollcall', participants:[...]}


The request message runs an http request from the server and stores and broadcasts the request name as a new message.

:request {name:[name], url:[url], [request options], responseType:[type], 
          responseName:[name], schedule:[schedule]}

request options are all the options from Node.js request object including method, headers, etc. If a URL is specified, it will overwrite these parameters. responseType is the type of the response message and responseName is the name it will be saved under if you would like to avoid saving a new response everytime the request is made.

Scheduled Messages

Chat.os provides a scheduling mechanism to act on messages at a regular interval. Normally this means the message will be repeatedly re-broadcast to its room, but request messages will be resent and the response will be sent to the room (allowing periodic queries to another server). The schedule is a 6 option cron specification for when the request should be made. See node-cron for details on the cron syntax.

Properties within scheduled messages can be replaced with the time the message is processed or a time before or after the current date. Any string found within the message that contains a pattern like


will be substituted with the current time altered by the time string. The format can be any valid format string according to date-time-format and the expression following the format specifies the years, months, days, hours, minutes and seconds to add or subtract from the current time. Some examples:

'The time is now %d{h:MM tt} on %d{mmmm d, yyyy}' -> 'The time is now 9:34 am on June 16, 2012'
'%d{yyyy-mm-dd HH:MM:ss}' -> '2012-06-16 09:34:14'
'%d{yyyy-mm-dd HH:MM:ss--1-0-0T0:0:0}' -> '2011-06-16 09:34:14'
'%d{yyyy-mm-dd HH:MM:ss--0-1-0T0:0:0}' -> '2012-05-16 09:34:14'
'%d{yyyy-mm-dd HH:MM:ss--0-0-1T21:34:14}' -> '2012-06-14 12:00:00'
'%d{yyyy-mm-dd HH:MM:ss++0-0-1T2:25:46}' -> '2012-06-17 12:00:00'
'%d{yyyy-mm-dd HH:MM:ss++0-2-0T0:0:0}' -> '2012-08-16 09:34:14'
'%d{yyyy-mm-dd HH:MM:ss++5-0-0T0:0:0}' -> '2017-06-16 09:34:14'

Writing Upgrades

The chat.os server provides very little functionality out-of-the-box. The goal is to build up rich interfaces by incrementally adding upgrades that deliver the missing functionality. Several upgrades have been documented in /example_upgrades for reference.

There a few functions in the chat.os namespace make upgrade programming possible, and a few more are available to keep the environment sane when upgrades are reloaded.


chat.os.send( text, message )

This method lets an upgrade send a message to the server as if it were submitted from the message input. If text is specified, the text will be added as the 'text' field of the context and the body of a comment if no message is provided. The contents of message may be explicitly specified by passing an object as the message parameter.

All messags will be saved to the room by default. If you would like to broadcast a message to the room that should not be saved (say, information about what a user is doing right now or individual game events), add persist:false to the message.


chat.os.addInputHandler( handler, priority )

function handler( message, next ) {
  if ( message.type != 'my-type' )
    return next();

  // do something with message and possibly call next()

An input handler receives a message coming from the server to the client and either modifies it or handles it. All messages are passed through each input handler, and the handler decides if it should act or not. Message processing will go through each input handler sequentially, and continue only if the handler calls the provided next function. If the message is the wrong type for the hander, it should call the next function and exit immediately. If the handler modifies or reads a message it expects to be handled elsewhere, it should always call the next function. Otherwise is should act on the message an return without calling next to prevent another handler (including the default handler) from acting on the message.

The priority parameter is optional and provides some order to the input chain even though multiple handlers may act on a message without being aware of each other. The higher the number the later the handler will be called, so you should specify a low number (say < 5) for handlers that act on the message but don't handle it, and a high number (say 5 > n >= 10) for handlers that handle the message (i.e. that do not call next). The default priority is 5.


chat.os.addOutputHandler( handler, priority )

function handler( context, next ) {
  if ( ! context.message || ! context.message.type != 'my-type' )
    return next();

  // do something with message and possibly call next()

Output handlers process messages before they leave the client for the server. They may be used to alter the message, or they may be used to implement new commands that only affect the current instance of the room. Like input handlers, output handlers must call next if the message is the wrong type or the handler wants the message to continue on to the server. The priority parameter also works as it does for input handlers.

The context object contains a 'text' and a 'message' property that correspond to the parameters supplied to the send function. At startup, an outputHandler will be added at priority 1 that will convert text parameters in the form :[type] [text] or :[type] [JSON] into a new message object. In the first case the message will be {type:[type], text:[text]} and in the second case, the message will simply be the JSON object with its type set to [type].


var safeHandler = chat.os.replaceSafe( name, f )
if ( saveHandler )
  element.bind( 'event', safeHandler );

The replaceSafe function can be used to create event handlers that can be attached to the global DOM (the DOM outside that owned by the upgrade) and yet be easily replaced when the upgrade is reloaded. This is necessary because most strategies for permitting multiple upgrades to listen to the same event do not make it easy to unload the event handler without having access to the instance of the function.

To use this function, pass in a name that uniquely identifies this handler (the name should be prepended with the upgrade name) and the handler. If replaceSafe has not seen the name before, it will return a wrapper function that behaves just like f. The upgrade should use this function as the eventHandler. If the replaceSafe function has already been called with this name it will return null. This indicates the function has been called before and the wrapper function is still listening for the event. The wrapper will now use the new function to process the event. If replaceSafe returns null, the upgrade should continue without binding anything to the event.

timing methods

chat.os.setInterval( upgrade, name, f, ms )
chat.os.setTimeout( upgrade, name, f, ms )
chat.os.requestAnimationFrame( upgrade, name, f )

These methods work just like their native counterparts. The only advantage to calling these is that the chat.os bootstrap code will be sure to clear all timing functions associated with an upgrade before the upgrade is replaced. The upgrade parameter must be the name of the upgrade, and the name parameter distinguishes functions within an upgrade.


chat.os.identity = {}; = 'name';
chat.os.upgrades = {};

The current user's identity (an object containing nickname, email, etc.), the name of the room, and a object containing all upgrades keyed by name are made availble for all upgrades to use.

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