如何向此腳本添加預加載？

Question

如何在此腳本中添加預加載gif，以便直到載入幻燈片中的所有圖像才顯示出來？

function slideSwitch() { 

var $active = $('#slideshow IMG.active'); 

if ($active.length == 0) $active = $('#slideshow IMG:last'); 

// use this to pull the images in the order they appear in the markup 
var $next = $active.next().length ? $active.next() 
    : $('#slideshow IMG:first'); 

// uncomment the 3 lines below to pull the images in random order 

// var $sibs = $active.siblings(); 
// var rndNum = Math.floor(Math.random() * $sibs.length); 
// var $next = $($sibs[ rndNum ]); 


$active.addClass('last-active'); 

$next.css({opacity: 0.0}) 
    .addClass('active') 
    .animate({opacity: 1.0}, 1500, function() { 
     $active.removeClass('active last-active'); 
    }); } 

$(function() { 
setInterval("slideSwitch()", 5000); 
}); 

Answer 1

預加載圖像可能是CSS背景圖像。加載圖像時，背景將不可見。