Question

I am trying to carry a class between li‘s with combine each() and eq() methods when buttons clicked. I am using same code with previous and next buttons except i+1 and i-1 but it is returning me different problems.

Here is jsFiddle to examine.

html:

<span class="prev">prev</span>
<ul>
    <li>0</li>
    <li>1</li>
    <li class="active">2</li>
    <li>3</li>
    <li>4</li>
</ul>
<span class="next">next</span>

jQuery:

var li = $('li');

$('.prev').click(function() {
    li.each(function(i) {
        if ( $(this).hasClass('active') ) {
            console.log(i);
            //this returning current true value = 2

            li.removeClass('active');
            li.eq(i-1).addClass('active');
            //this is working better
            //problem is: not selecting 4
        }
    });
});

$('.next').click(function() {
    li.each(function(i) {
        if ( $(this).hasClass('active') ) {
            console.log(i);
            //this returning current true value = 2

            //problem starts:
            //li.removeClass('active');
            //when this is active; all active classes are gone

            li.eq(i+1).addClass('active');
            //try to select next 'li' here
            //but it is selecting all li's bigger than current value
        }
    });
});

Answer 1

If for some reason you need the index, you could always do:

$('.prev').on('click', function() {
    var i = $(".active").index();
        i--;
    $(".active").removeClass('active');
    $('li').eq(i).addClass('active');
});

$('.next').on('click', function() {
    var i = $(".active").index();
        i = i >= $('li').length-1 ? 0 : i+1;
    $(".active").removeClass('active');
    $('li').eq(i).addClass('active');
});​

FIDDLE

If not :

$('.prev, .next').on('click', function() {
    if ($(".active")[$(this).attr('class')]().index()!=-1)
    $(".active").removeClass('active')[$(this).attr('class')]().addClass('active');
});

FIDDLE