Background slideshow (javascript) fade transition effect

I am trying to apply the fade effect to the javascsript background slideshow. When I changed the value, JS ignored it. I tried fadeIn and fadeOut. What is wrong with this code?

var bgimages=new Array()
bgimages[0]="tenis.jpg"
bgimages[1]="rtrr.jpg"
bgimages[2]="tenis.jpg"

//preload images
var pathToImg=new Array()
for (i=0;i<bgimages.length;i++) {
    pathToImg[i]=new Image()
    pathToImg[i].src=bgimages[i]
}
var inc=-1

function bgSlide() {
    if (inc<bgimages.length-1)
        inc++
    else
        inc=0

    document.body.background=pathToImg[inc].src
}

if (document.all||document.getElementById)
    window.onload=new Function('bgSlide(); setInterval("bgSlide()",3000),fade(2000)')

Solution

You can not fade background images. You can fade images in <img> tags.

Here is my jsFiddle DEMO.

Here is some sample code (including JQuery, CSS, and HTML):

<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>Untitled Document</title>
<style>
img{
    position:absolute;
    top:0;
    display:none;
    width:auto;
    height:100%;
}
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>
function fader() {
    $("img").first().appendTo('#wrap').fadeOut(3000);
    $("img").first().fadeIn(3000);    
    setTimeout(fader, 4200);
}
</script>
</head>
<body onLoad="fader();">
<div id="wrap">
<img src="http://stats.hashweb.org/static/img/jsfiddle-logo.png">
<img src="http://startbootstrap.com/templates/freelancer/img/profile.png">
<img src="http://www.silvercoinstoday.com//images/Silver-Element-Atomic-Structure.jpg">
</div>
</body>
</html>