If element changed class from one to another in jQuery

The easiest way to do this, based on what I understand, your question to look at is to put a handler on the index buttons and a method to track the current image.

Hear the slide change

var currentSlide = '';

$('.slideIndexButtons').on('click', function(e){
    // Conditional logic that compares $(this).data('whichimage') to currentSlide
    var whichImage = $(this).data('whichimage');

    // ->this means attaching data-whichimage="" to each of the elements, or
    // ->you can just stick with detecting the class and going from there
    // Either process results in isBackwards boolean

    if (currentSlide == 'prev' && whichImage == 'current') {
        isBackwards = true;
    }

    if (isBackwards) {
        // Backwards logic here
    } else {
        // Other logic here
    }

    // Unless the event we're listening for in keeping currentSlide updated is also fired when
    // the slide changes due to user input, we'll need to update currentSlide manually.
    currentSlide = whichImage; 
});

      

        
        
        
      

    

Track the current slide

$('#slider').on('event', function(){
    // This is assuming that we're strictly listening to the slider automatic sliding

    // The event you attach this to is either fired before or after the slide changes.
    // Knowing which is key in getting the data you want. You are either getting
    // The data from this slide $(this).data('whichimage') or 
    // $(this).next().data('whichimage')

    // Again, you can go with classes, but it is a lot of logic which you have to 
    // update manually if you ever have to add or alter an image in the slide set.
    // Either way, you end up with the variable targetImage

    currentSlide = targetImage;
});

      

        
        
        
      

    

Either way, your slideshow code has an API that will allow you to listen when slide events are fired. Otherwise, you will need to find a way to configure, fire and listen for these events manually, either through callbacks passed in or through (eek!) Modifying the code and possibly inadvertently changing its functionality.

This should give you what you asked for. Let me know how it goes.

You can add this line at the very beginning of the slideTo function in your cycle.js file

if((idx < index && !(idx == 0 && index == antall - 1)) ||
   (idx == antall - 1 && index == 0)){
   jQuery.trigger('BACKWARDS')
}

      

        
        
        
      

    

and then add an event handler for "BACKWARDS" elsewhere (perhaps at the end of the .js loop?).

jQuery.on('BACKWARDS', function(e){
   //DO THINGS HERE
}