JavaScript/jQuery를 사용하여 원활한 무한 루프 이미지 슬라이더를 얻는 방법은 무엇입니까?

$(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 });
            }
        });   
     }
    
  });
});