For JavaScript, here is the code we recommend for generating, persisting and retrieving a UUID. This could be wrapped in a function can called directly from the PUBNUB.init function rather than the two step inline solution below.
// get/create/store UUID
var UUID = PUBNUB.db.get('session') || (function(){
var uuid = PUBNUB.uuid();
PUBNUB.db.set('session', uuid);
return uuid;
})();
// init PUBNUB object with UUID value
var pubnub = PUBNUB.init({
publish_key: pubKey,
subscribe_key: subKey,
uuid: UUID
});