setInterval run fast after 5-7 minutes

Why does setInterval run very fast after some time? I used the code below for a background slideshow on my 开发者_StackOverflow社区site. I also use the fullpage preloader plugin.

function slideSwitch() {
    var $active = $('#slideshow IMG.active');
    if ( $active.length == 0 ) $active = $('#slideshow IMG:last');
    var $next =  $active.next().length ? $active.next() : $('#slideshow IMG:first');
    $active.addClass('last-active');
    $next.css({opacity: 0.0})
        .addClass('active')
        .animate({opacity: 1.0}, 1000, function() {
            $active.removeClass('active last-active');
        });
}

$(function() {
    setInterval( "slideSwitch()", 9999);
});

//use fullpage preloader
QueryLoader.init();

I want to repeat the animation every 9999 milliseconds. But after some time (5-7 minutes), the animation seems to repeat every 1000 milliseconds.

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You might want to make sure that one animation doesn't interrupt the previous one in a way you're not intending:

...
$next.css({ opacity: 0.0 })
     .addClass('active')
     .stop() // <-- new line
     .animate({ opacity: 1.0}, 1000, function() {
         $active.removeClass('active last-active'); 
     });

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the javascript function setInterval() returns a handle

handle = setInterval("slideSwitch()", 9999);

that you can clear whenever you want with clearInterval

function killInterval(){
   clearInterval(handle);
}

So you'd have to clean your interval after some time, for that you want to use setTimeout

setTimeout("killInterval()",3000);

---

setInterval will run the function every 9999 milliseconds, not once.

setInterval will repeat, setTimeout will run once.

You need to use setTimeout.