preach

Preach is a lightweight pubsub utility for node and the browser. The browser version is ~2kb gzipped.

Installation

For node

npm install preach --save

For browsers

bower install preach

or

git clone [e-mail]:zeusdeux/preach.git

If you plan to use it with browserify, then just require index.js. If you plan to use it directly in the browser, then include browser/preach.min.js. This will export a global require function. You can then do:

<script>
  var Preach = require('Preach');
  var preachInstance = new Preach;
</script> 

Changelog

• 0.3.0
  • Preach is now a lot more forgiving (no more throws, yay!)
• 0.2.0
  • Preach now exports a constructor when require-ed instead of a monolithic instance (incompatible change)
• 0.1.0
  • Initial version

API

• Preach.prototype.pub( channel, [data], [data], [...] )
• Preach.prototype.sub( channel, subscriber )
• Preach.prototype.unsub( channel, subscriber )
• Preach.prototype.purge()
• Preach.prototype.channels()
• Preach.prototype.subscribers( channel )
• Preach.prototype.subscriberCount( channel )
• Preach.prototype.setMaxSubscribers( n )

Preach.prototype.pub(channel, [data], [data], [...])

This method is used to publish data to channel.

This method takes the following parameters:

• channel: String channel name or a regular expression (RegExp)
• data : Any valid javascript value. Also, this is an optional parameter

Example:

var preach = new Preach;
preach.pub('channel1');
preach.pub('channel2', 1234);
preach.pub('channel3', {a: 100}, 'test');
preach.pub(/^channel.*/, 10, {a: 'boop'}); //will publish data to all channels beginning with 'channel'

Preach.prototype.sub(channel, subscriber)

This method is used to add a subscriber to channel.

This method takes the following parameters:

• channel : String channel name or a regular expression (RegExp)
• subscriber : A valid Function. This Function is called whenever data is published to the channel.

A subscriber can subscribe to as many channels as required and even publish to any channel.

Note:

If a subscriber publishes to a channel that it is subscribed to, then that will result in infinite recursion.

Example:

var preach = new Preach;
preach.sub('channel1', console.log.bind(window.console)); //true
preach.sub(/^channel.*/, function(){
  console.log('I will get subscribed to any existing channel that has a name starting with the string "channel"');
}); //true

Note:

If a String is passed as channel and there are no channels that match it, then a new channel will be created and subscriber will be subscribed to it.

Preach.prototype.unsub(channel, subscriber)

This method is used to unsubscribe a subscriber from channel.

This method takes the following parameters:

• channel : String channel name or a regular expression (RegExp)
• subscriber : A valid Function. This Function is removed as a subscriber of channel

Example:

var preach = new Preach;
preach.sub('channel1', console.log.bind(window.log)); //true
preach.unsub('channel1', console.log.bind(window.log)); //true
 
preach.sub('test1', function(){}); //true
preach.sub('test2', function(){}); //true
preach.unsub(/.*/, function(){}); //true
                                  //function(){} is now unsubscribed from *all* channels

Preach.prototype.purge()

This method purges all channels and their subscribers and gives you a fresh Preach instance to work with. This method is quite destructive and hence caution is advised in its usage.

Example:

var preach = new Preach;
preach.sub('test1', function(){});
preach.sub('test2', function(){});
preach.channels(); //["test1", "test2"]
preach.subscribers(); //Object {test1: Array[1], test2: Array[1]}
preach.purge(); //PURGE! return val -> true
preach.channels(); //[]
preach.subscribers(); //{}

Preach.prototype.channels()

This method returns an array of the current active channels.

var preach = new Preach;
preach.sub('test1', function(){}); //true
preach.sub('test2', function(){}); //true
preach.channels(); //["test1", "test2"]

Preach.prototype.subscribers(channel)

This method returns information about the subscribers for a channel.

This method takes the following parameter:

• channel : String channel name or a regular expression (RegExp) Not providing a value for channel is the same as passing /.*/ i.e., basically "GET ALL THE CHANNELS AND THEIR SUBSCRIBERS!".

Example:

var preach = new Preach;
preach.sub('test1', function(){});
preach.sub('test2', function(){});
preach.subscribers(); //Object {test1: Array[1], test2: Array[1]}
preach.subscribers('test1'); //Object {test1: Array[1]}

Note:

If a RegExp or String is passed as channel and there are no channels that match it, then Preach.subscribers returns an empty object ie {} and does not throw.

Preach.prototype.subscriberCount(channel)

This method returns the no of subscribers a channel has.

This method takes the following parameter:

• channel : String channel name or a regular expression (RegExp) Not providing a value for channel is the same as passing /.*/ i.e., basically "GET THE SUBSCRIBER COUNT FOR ALL THE CHANNELS".

Example:

var preach = new Preach;
preach.sub('test1', function(){});
preach.sub('test1', function(d){ console.log(d); });
preach.sub('test2', function(){});
preach.subscriberCount(); //Object {test1: 2, test2: 1}
preach.subscriberCount('test2'); //Object {test2: 1}
preach.subscriberCount(/1$/); //Object {test1: 2}

Note:

If a RegExp or String is passed as channel and there are no channels that match it, then Preach.subscriberCount returns an empty object ie {} and does not throw.

Preach.prototype.setMaxSubscribers(n)

This sets the max listeners for each channel at n. Default is unlimited which is set by making n zero. This can also be set during Preach initialization.

var preach = new Preach;
preach.setMaxSubscribers(10);
//analogous to
var preach = new Preach(10);

Note:

If n is lesser than zero then Preach will throw.