图像旋转器的奇怪问题

Question

基本上，下面的代码会淡入淡出图像。它工作正常，但在测试中，其中一个在他的计算机上测试它的人离开主页为... IDK ...说20分钟。当他回到电脑前时，图像的旋转时间不到一秒钟。

此代码中的任何内容是否都会导致此问题？

function theRotator() {
    //Set the opacity of all images to 0
    $('div.rotator ul li').css({opacity: 0.0});

    //Get the first image and display it (gets set to full opacity)
    $('div.rotator ul li:first').css({opacity: 1.0});

    //Call the rotator function to run the slideshow, 6000 = change to next image after 6 seconds
    setInterval('rotate()',4000);
}

function rotate() {
    //Get the first image
    var current = ($('div.rotator ul li.show')? $('div.rotator ul li.show') :    $('div.rotator ul li:first'));

    if ( current.length == 0 ) current = $('div.rotator ul li:first');

    //Get next image, when it reaches the end, rotate it back to the first image
    var next = ((current.next().length) ? ((current.next().hasClass('show')) ? $('div.rotator ul li:first') :current.next()) : $('div.rotator ul li:first'));

    //Un-comment the 3 lines below to get the images in random order
    //var sibs = current.siblings();
    //var rndNum = Math.floor(Math.random() * sibs.length );
    //var next = $( sibs[ rndNum ] );

    //Set the fade in effect for the next image, the show class has higher z-index
    next.css({opacity: 0.0})
        .addClass('show')
        .animate({opacity: 1.0}, 1000);

    //Hide the current image
    current.animate({opacity: 0.0}, 1000)
        .removeClass('show');
};

$(document).ready(function() {
    //Load the slideshow
    theRotator();
    $('div.rotator').fadeIn(1000);
    $('div.rotator ul li').fadeIn(1000); // tweek for IE
});