var NumOfCovers = 4;
var coverList = [
'bs1a',
'bs1b',
'bs1c',
'bs1d',
'bs1e',
'bs1f',
'bs2a',
'bs2b',
'bs2c',
'bs2d',
'bs2e',
'bs2f',
'bsnf1a',
'bsnf1b',
'bsnf1c',
'bsnf1d',
'bsnf1f',
'bsnf1g',
'bsnf2a',
'bsnf2b',
'bsnf2c',
'bsnf2d',
'bsnf2e',
'bsnf2f',
'bsnf2g',
'bsnf2h',
'bsnf3a',
'bsnf3b',
'bsnf3c',
'bsnf3d',
'bsnf3e',
'bsnf3f',
'bsnf3g',
'bsnf3h',
];

//=========================================================

for (var i=0; i<NumOfCovers; ++i) {
	getACoverCode(i+1);
}
function getACoverCode(booknum) {
	var now = new Date();
	var seed = now.getSeconds();
	var random_number = Math.random(seed);
	var range = random_number * coverList.length;
	var rounded_number = Math.round(range);
	if (rounded_number == coverList.length){rounded_number = 0;}
	
	//<img id="Book1" src="/images/home_book_bsnf3a.jpg" alt="Book 1" height="165" />
	document.getElementById('book'+booknum).src = "/images/home_book_" + coverList[rounded_number] + ".jpg";
	
	coverList.splice(rounded_number,1);
}