postal.js/src/ChannelDefinition.js

var ChannelDefinition = function ( channelName ) {
	this.channel = channelName || DEFAULT_CHANNEL;
};

ChannelDefinition.prototype.subscribe = function () {
	return arguments.length === 1 ?
	       new SubscriptionDefinition( this.channel, arguments[0].topic, arguments[0].callback ) :
	       new SubscriptionDefinition( this.channel, arguments[0], arguments[1] );
};

ChannelDefinition.prototype.publish = function () {
	var envelope = arguments.length === 1 ?
	                (Object.prototype.toString.call(arguments[0]) === '[object String]' ?
                  { topic: arguments[0] } : arguments[0]) : { topic : arguments[0], data : arguments[1] };
	envelope.channel = this.channel;
	return postal.configuration.bus.publish( envelope );
};