Infinity Loop Slider Concepts

This article discusses the best practices, such as readability, code reusability, and good coding practices, for building an Infinity-Image-Loop-Slider for a website using JavaScript/jQuery. The focus is on how to arrange the pictures to create the illusion of an unending loop slider.

Implementing an Infinity Loop Slider

One straightforward method for creating an infinite image slider is as follows: Assume you have "n" images to slide in a loop, with the first image following the nth image and vice-versa. Create a clone of the first and last images and do the following:

• Append the clone of the last image before the first image.
• Append the clone of the first image after the last image.

Regardless of the number of images, you only need to insert two cloned items at most.

Assuming all images are 100px wide and displayed within a container with overflow: hidden, display: inline-block, and white-space: nowrap, the container holding the images can be easily aligned in a row.

For n = 4, the DOM structure would appear as follows:

offset(px)     0       100     200     300     400     500
images         |   4c   |   1   |   2   |   3   |   4   |   1c
                                                   
/*                 ^^                                       ^^
       [ Clone of the last image ]              [ Clone of the 1st image ]
*/

Initially, the container is positioned with left: -100px, allowing the first image to be displayed. To switch between images, apply a JavaScript animation to the CSS property you originally selected.

• When the slider is on the 4th image, moving to image 1c involves animating from image 4 to 1c. Once the animation is complete, instantly reposition the slider wrapper at the actual offset of the 1st image (e.g., set left: -100px to the container).
• Similarly, when the slider is positioned on the 1st element, performing the previous animation from image 1 to 4c and moving the container to the 4th image offset (left: -400px to the container) is sufficient to display the previous image.

Orchestrating the Slide Loop

The accompanying fiddle demonstrates this effect. Below is the basic JavaScript/jQuery code used:

$(function() {
 
  var gallery = $('#gallery ul'),
      items   = gallery.find('li'),
      len     = items.length,
      current = 1,  /* the item we're currently looking */
      
      first   = items.filter(':first'),
      last    = items.filter(':last'),
      
      triggers = $('button');
  
  /* 1. Cloning first and last item */
  first.before(last.clone(true)); 
  last.after(first.clone(true)); 
  
  /* 2. Set button handlers */
  triggers.on('click', function() {

    var cycle, delta;
    
    if (gallery.is(':not(:animated)')) {
     
        cycle = false;
        delta = (this.id === "prev")? -1 : 1;
        /* in the example buttons have id "prev" or "next" */  
    
        gallery.animate({ left: "+=" + (-100 * delta) }, function() {
      
            current += delta;
       
            /** 
             * we're cycling the slider when the the value of "current" 
             * variable (after increment/decrement) is 0 or when it exceeds
             * the initial gallery length
             */          
            cycle = (current === 0 || current > len);
       
            if (cycle) {
                /* we switched from image 1 to 4-cloned or 
                   from image 4 to 1-cloned */
                current = (current === 0)? len : 1; 
                gallery.css({left:  -100 * current });
            }
        });   
     }
    
  });
});

Conclusion

This solution is relatively straightforward and efficient, requiring only two additional DOM insertion operations and simple loop management logic compared to a non-looping slider.

While alternative approaches may exist, this method provides a practical and effective solution for creating an infinity loop slider.

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