final.

gistfile1.js

function Advertisement(category,media_id,frequency,duration){
	this.category	= category,
	this.media_id	= media_id;
	this.frequency	= frequency;
	this.duration	= duration;
	this.getAds		= function(){
		var ads = [{time : 0, adTagUrl : this.getVast("preRoll")}];
		var midrollCount = parseInt(this.duration/this.frequency);
		for(i=1;i<=midrollCount;i++){
			var midroll = {
				time : i*this.frequency,
				adTagUrl : this.getVast("midRoll"+i)
			};
			ads.push(midroll);
		};
		ads.push({time : -1, adTagUrl : this.getVast("postRoll")});
		return ads;
	};
	this.getVast	= function(identifier){
		return 'http://www.vomedia.tv/AdServer/mobile.php?category='+this.category+'&mediaid='+this.media_id+'&channel='+this.channel+'&publisherid=vidivodo&viewType?'+identifier;
	};
}