You can use JSON to send multiple data values in one string. In the following code example, JSON is used to create a set of name-value pairs to represent latitude and longitude coordinates.

// Create the JSON string.
var latLonStr = "{'lat':'47.7575', 'lon':'-122.24278'}";

// Use the eval function to convert the string back into an object.
// This would typically be used on the receiving side.
var latLonObj = eval('(' + latLonStr + ')');

// Test it out using an alert.
alert('latitude: ' + latLonObj.lat + ', longitude: ' + latLonObj.lon);

For more information, see the JSON Web site.

The following procedures walk you through the individual steps of implementing custom presence.

1. In your JavaScript file, declare a variable containing the extension name.

2. This value must be unique within the application and must not exceed 64 characters.

   var extensionName = 'com.example.ExtNm';

3. Create the necessary code for the functionality of the extension.

4. In this particular example, the extension stores a name-value pair. The function is used as a constructor, and the other functions in the class are defined by using the prototype property.

   function MyPresenceExtension(name, content)
   {
       this.name = name; 
       this.content = content;
   }
   MyPresenceExtension.prototype.get_name = function() {
       return this.name;
   }
   MyPresenceExtension.prototype.get_content = function() {
       return this.content;
   }

1. Declare the PresenceExtensionFactory object.

   This object serializes and deserializes your custom presence extension.

   MyPresenceFactory = function () {}

2. Create the serialize and deserialize functions.

   MyPresenceFactory.prototype.serialize = function(prop) {
       return prop.get_content();
   }
   MyPresenceFactory.prototype.deserialize = function(name, content) {
       return new MyPresenceExtension(name, content);
   }

• Add the presence factory to the user object by calling set_presenceFactory, and then creating a new instance of MyPresenceFactory.

  User.set_presenceFactory(new MyPresenceFactory());

1. Add the custom presence extension for the signed-in user.

   function addCustomPresence() 
   {
       endpointCollection = _user.get_endpoints();
       endpointPresence = endpointCollection.get_item(0).get_presence();
       extensionCollection = endpointPresence.get_extensions();
       extensionCollection.add(new MyPresenceExtension(extensionName, '*'));
   }

2. Add code to check for the presence extension in each endpoint of this contact's presence.

   function getCustomPresenceContent(address) 
   {
       endpointEnum = address.get_endpoints().getEnumerator();
       while (endpointEnum.moveNext()) 
       {
           endpoint = endpointEnum.get_current();
           extensionEnum = endpoint.get_presence().get_extensions().getEnumerator();
           while (extensionEnum.moveNext()) 
           {
               extension = extensionEnum.get_current();
               if (extension.get_name() == extensionName) 
               {
                   return extension.get_content();
               }
           }
       }
       return '';
   }

The following example demonstrates the complete process for implementing the example name-value custom presence extension.

// **** CUSTOM PRESENCE ****
MyPresenceFactory = function () {}
MyPresenceFactory.prototype.serialize = function(prop) {
    return prop.get_content();
}

MyPresenceFactory.prototype.deserialize = function(name, content) {
    return new MyPresenceExtension(name, content);
}

var extensionName = 'MLSDK';
   
function MyPresenceExtension(name, content)
{
    this.name = name; 
    this.content = content;
}

MyPresenceExtension.prototype.get_name = function() {
    return this.name;
}

MyPresenceExtension.prototype.get_content = function() {
    return this.content;
}

/* Add a custom presence extension to the signed-in user */
function addCustomPresence()
{
    endpointCollection = _user.get_endpoints();
    endpointPresence = endpointCollection.get_item(0).get_presence();
    extensionCollection = endpointPresence.get_extensions();
    extensionCollection.add(new MyPresenceExtension(extensionName, '*'));
}      

// For each endpoint of this contact's presence, check for presence extension
function getCustomPresenceContent(address)
{
    endpointEnum = address.get_endpoints().getEnumerator();
    while (endpointEnum.moveNext())
    {
        endpoint = endpointEnum.get_current();
        extensionEnum = endpoint.get_presence().get_extensions().getEnumerator();
        while (extensionEnum.moveNext())
        {
            extension = extensionEnum.get_current();
            if (extension.get_name() == extensionName)
            {
                return extension.get_content();
            }
        }
    }
    return '';
}
// **** END CUSTOM PRESENCE ****

Concepts