$(document).ready(function(){
	
  var i;
  for (i = 97; i < 101; i++) {
    $("li a.overflow[data-select=" + i + "]").css({"display" : "block" , "opacity" : "1"});
  }   
  
  zaehler = 97;	  
  var counter = new Array();
  
  $( "a.verk_bM_Liste_next" ).on( "click", function() {
 
	var ArtNr = $(this).attr("data-ArtNr");

	if(counter.some(item => item.Nr === ArtNr)){
	$.each( counter, function() {
	    if (this.Nr == ArtNr) {
	        this.Zaehler = zaehler;
	    }
	});
	}
	else{
		counter.push({
            Nr: ArtNr,
            Zaehler: 97
        });  
	};
	
    for (var i = 0, theindex = -1; i < counter.length && theindex == -1; i++) {
        if (counter[i].Nr == ArtNr) {
            theindex = i;
        }
    }
	
    zaehler = counter[theindex].Zaehler;
    console.log(zaehler);

	var anzahl = $("ul#UL_" + ArtNr).children().length; // zählen der Listeneinträge
	var slides = anzahl / 4;

	if (zaehler < anzahl + 93){ 

      for (i = zaehler; i < zaehler + 4; i++) {  
        $("ul#UL_" + ArtNr + " li a.overflow[data-select=" + i + "]").css({"display" : "none" , "opacity" : "0"});
      }
    
      zaehler = zaehler + 4;
      for (i = zaehler; i < zaehler + 4; i++) {
        $("ul#UL_" + ArtNr + " li a.overflow[data-select=" + i + "]").css({"display" : "block" , "opacity" : "1"});
      }
    }
  });
  
  $("a.verk_bM_Liste_prev").on("click", function(){
	  
		var ArtNr = $(this).attr("data-ArtNr");
		Array.push(ArtNr); 
		first = Array.shift();
		if(Array != first) {zaehler = 97};
		var anzahl = $("ul#UL_" + ArtNr).children().length; // zählen der Listeneinträge
		var slides = anzahl / 4;

    if (zaehler > 100){  // 105
      for (i = zaehler; i < zaehler+5; i++) {  
		$("ul#UL_" + ArtNr + " li a.overflow[data-select=" + i + "]").css({"display" : "none" , "opacity" : "0"});
	  }
      
	  zaehler = zaehler-1; //104
	  for (i = zaehler; i > zaehler-4; i--) { 
	    $("ul#UL_" + ArtNr + " li a.overflow[data-select=" + i + "]").css({"display" : "block" , "opacity" : "1"});
	  }
	}
    if(zaehler > 99){
    zaehler = zaehler-3;
    }
  });
});