Question

I have a custom made slideshow object to perform the usual stuff the name indicates on a website. It all works well except when I switch tabs in Chrome and come back to the website tab. When that happens, the slideshow goes nuts and starts fading the images disregarding the setInterval interval given. Can’t find anyhing related to this, so I’d like to at least know if it’s a problem with the code or a software issue.

Here’s the code (being used with jQuery) :

$(function() {

    // slideshow
    var slideshow = {
        id : false,
        current : 0,
        count : 0,
        interval : false,
        init : function(data) {
            if (!data)
                return false;

            $.each(data, $.proxy(
                function(index, value) {
                    this[index] = data[index];
                }, this)
            );

            this.count = this.images.length;

            for (x=1;x<=this.count;x++)
                $('#slider ul.nav').append('<li></li>');

            $('#slider ul.nav li').live('click', function()
            {
                slideshow.click(this);
            });

            $('#slider ul.nav li:eq(0)').addClass('on');
            $('#slider ul.nav').css('width', (15*this.count)+'px');

            return true;
        },
        start : function () {
            slideshow.id = setInterval(function() { slideshow.action(); }, slideshow.options.interval);
        },
        stop : function() {
            clearInterval(slideshow.id);
        },
        action : function() {
            slideshow.current < (slideshow.count-1) ? slideshow.current++ : slideshow.current = 0;

            $('#slider img').fadeOut('normal', function() {
                $('#slider img').attr('src', slideshow.images[slideshow.current].url);
                $('#slider ul.nav li').removeClass('on');
                $('#slider ul.nav li:eq('+slideshow.current+')').addClass('on');
                $('#slider div.title').html(slideshow.images[slideshow.current].title);
                $('#slider div.description').html(slideshow.images[slideshow.current].description);
                $('#slider a.more').attr('href', slideshow.images[slideshow.current].target);
            }).fadeIn('normal');

            return true;
        },
        click : function(o) {
            slideshow.stop();

            var index = $('#slider ul.nav li').index(o);
            slideshow.current = index;

            $('#slider img').fadeOut('normal', function() {
                $('#slider img').attr('src', slideshow.images[index].url);
                $('#slider ul.nav li').removeClass('on');
                $(o).addClass('on');
                $('#slider div.title').html(slideshow.images[index].title);
                $('#slider div.description').html(slideshow.images[index].description);
                $('#slider a.more').attr('href', slideshow.images[index].target);
            }).fadeIn('normal');

            slideshow.start();
            return true;
        },
    };

    slideshow.init(slider);
    slideshow.start();

});

Answer 1

I’d favour using setTimeout() repeatedly over using setInterval() – so many things can go wrong with setInterval() and you don’t know how busy the browser is and whether the interval is realistic.

Browsers don’t honour your chosen timeout or interval exactly. This is mainly for security; to prevent a flood of events from messing with the browser’s ability to function normally. Chrome is better about honouring timers more accurately, though it does still slow them down significantly when a tab is in the background (see this answer), for example.

If you set a new timer with setTimeout during your existing call to slideshow.action(), then you won’t get events queuing up when your browser can’t quite keep up, but it will still go nice and quickly when the browser is able to do so.

You will still be able to stop the timer using the timer ID, that ID will just change often.