//global vars
var numOfImages = 4;
var subDirectory = "images/banner_";
var imgType = '.jpg';

var thisAd = 0;

//the code
var images = new Array(numOfImages);


//create the loop to load each image into a new image var
for(var i=0; i<images.length; i++) {
	images[i] = new Image();
	images[i].src = subDirectory +i + imgType;
}

rotate_banners = function imageRandomizer(){

	thisAd = Math.floor(Math.random()*images.length);
	var targetImgElement = document.getElementById('banner');
	targetImgElement.src = images[thisAd].src;

	rotate();
}

function rotate() {
	thisAd++;

	if (thisAd == images.length) {
		thisAd = 0;
	}

	var targetImgElement = document.getElementById('banner');
	targetImgElement.src = images[thisAd].src;


	setTimeout(rotate, 5 * 1000);
}

window.onload=rotate_banners;