XCVR

XCVR (pronounced Tranz-see-ver) is a message channel for sending messages within an application.

It is designed to work in both node.js and in browser.

It is intended to be used as a communications channel between various elements of an application. It provides a mechanism for subscribing to and sending messages with a named type and an optional message payload (which can be a string, or a more complex type such as an object)

Messages can be sent by one portion of a system without knowing what might be listening for that message. Likewise, messages can be received without advanced knowledge of what the origin of the message is.

This makes XCVR and ideal mechanism for providing loose coupling between application components.

Usage

// In browser the initial XCVR object is created for you.
// In node.js, however, you have to create an XCVR object
var xcvr = require('XCVR');
var XCVR = new xcvr();

// set up a receiver for a particular message 
XCVR.receive('greeting_message', function greeting_handler(msg) {
    console.log('received message:' + msg);
});

// send a message
XCVR.send('greeting_message', "Hi there");

// listen for a particular message type only once:
XCVR.receive_once('link_terminated', function(msg) {
    console.log('our link was terminated, shutting down');
    do_shutdowny_things();
});

// Remove a message receiver we added earlier
XCVR.remove_receiver('greeting_message', greeting_handler)

The XCVR object acts as a transciever and is used to send and receive messages across the application. Sent messages are delivered automatically to anything that is listening for that type of message.

The messages are delivered asyncronously, so the call to send the message returns immediately, prior to each message recipient being called. Messages are also protected against receivers exceptions, that is to say that if there is an exception in a receiver it will not stop or otherwise prevent delivery to other receivers of the same message type;

In the browser environment, a usable XCVR is created automatically.
This XCVR object can then be used by whatever code needs to send and receive messages.

In the node.js environment, you can create multiple XCVR objects if you choose. When you do this, each XCVR object creates an independent communication channel, which is completely isolated from other XCVR objects.