jQuery Cycle - How to change class of element based on active slide

Question

I have a sideshow using jQuery Cycle . The way it works is that clicking the .next or .prev divs cycles through the slideshow as expected. What I need it to do though is to have it update the UL in .timeline_pagination and add/remove the class 'active' to the corresponding slide. eg. if the #tl_2004 slide is active, the then #goto2004 li needs the class active. I do not want or need the #goto*** to be functional, they're purely there as a display reference.

Thanks for your help in advance.

Here is the markup:

<!-- FAKE PAGINATION -->    
<div class="timeline_pagination">
        <ul>
            <li class="active" id="goto1994">1994</li>
            <li id="goto2000">2000</li>
            <li id="goto2004">2004</li>
            <li id="goto2007">2007</li>
        </ul>
</div>
<!-- END FAKE PAGINATION --> 

<div class="timeline_slideshow">
    <div class="prev"></div>
    <div class="next"></div>
    <div class="tl_slideshow">

        <div id="tl_1994">
            <div class="caption">
                <h4>title</h4>
                <p>my text</p>
            </div>
        </div>

        <div id="tl_2000">
            <div class="caption">
                <h4>title</h4>
                <p>my text</p>
            </div>
        </div>

        <div id="tl_2004">
            <div class="caption">   
                <h4>title</h4>
                <p>my text</p>
            </div>
        </div>

        <div id="tl_2007">
            <div class="caption">
                <h4>title</h4>
                <p>my text</p>
            </div>
        </div>

    </div>
</div>

Here is the javascript:

$('.tl_slideshow').cycle({
        fx:         'scrollHorz',
        next:       '.next', 
        prev:       '.prev',
        timeout:    0,
        speed:      750,
        nowrap:     1,
        after:      onAfter
});

function onAfter(curr, next, opts) {
    var index = opts.currSlide;
    $('.prev')[index == 0 ? 'fadeOut' : 'fadeIn']();
    $('.next')[index == opts.slideCount - 1 ? 'fadeOut' : 'fadeIn']();
}

Answer 1

Try with this jquery code

var PREFIX_ID_PAGINATION = "goto";
var PREFIX_ID_SLIDESHOW = "tl_";

$('.tl_slideshow').cycle({
        fx:         'scrollHorz',
        next:       '.next',
        prev:       '.prev',
        timeout:    0,
        speed:      750,
        nowrap:     1,
        after:      onAfter
});

function onAfter(prev, current, opts) {
    var index = opts.currSlide;
    $('.prev')[index == 0 ? 'fadeOut' : 'fadeIn']();
    $('.next')[index == opts.slideCount - 1 ? 'fadeOut' : 'fadeIn']();

    var current_id = $(current).attr('id');
    if( current_id.match("^" + PREFIX_ID_SLIDESHOW + "[0-9]+$")){
        $('li.active').removeClass('active');
        $('#' + PREFIX_ID_PAGINATION + current_id.replace(PREFIX_ID_SLIDESHOW,"")).addClass('active');
    }
}

There is a jsfiddle example here