How a JSONP WSs understand gives really tweets without page reload


#1

how a JSONP WSs understand gives really tweets without page reload? I put tweets in a select tag but sometimes remain from old twitterID tweets on page, and can not understand from select.length if the new id really gives tweets or nothing?

var url = "https://api.twitter.com/1/statuses/user_timeline/"+tidsValue+".json?callback=updateTweets" +"&random=" + (new Date()).getTime(); 

also I may understand if a @twiterId exist NOT?


#2