jquery .prepend cloning error

Question

I'm attempting to add an item to my navigation bar when the screen is < 480px and the scroll is > 80. Multiple copies of this item are being inserted into my main-nav. could someone please help me understand why that is happening? You can see what's happening by going here.

$(function () {
    var $window = $(window);
    var $width = $(window).width();

    function windowWidth() {
        if ($width < 480) {
            function top() {
                var $top = $window.scrollTop();
                if ($top < 80) {
                    $(".main-nav").css({
                        'position': '',
                        'width': '99.5%'
                    });
                    $(".thick-line-header").css("display", "");
                } else {
                    var $homeTab = $('<li class="home"><a href="#top" >test</a></li>');
                    $(".main-nav li").css({
                        'position': 'fixed',
                        'width': '100%',
                        'top': '0',
                        'left': '0',
                        'margin-top': '0'
                    });
                    $("#main-nav").prepend($homeTab);
                    $(".thick-line-header").css("display", "none");
                }
            };
            $(window).scroll(top);
        }
    };
    windowWidth();
});

Answer 1

I tried to reproduce your bug but I got no chance, maybe I am missing something Anyway I guess you need to add a flag weather the data has been added before or not because your condition is true more than one time and while you are scrolling

var added = false; 
$(function() {
    var $window = $(window);
    var $width = $(window).width();
    function windowWidth() {
        if ( $width< 480 ) {
            function top() {
                var $top = $window.scrollTop();
                if( $top < 80 ) {
                   $(".main-nav").css({
                      'position': '',
                      'width': '99.5%'
                   }); 
                   $(".thick-line-header").css("display",""); 
                }
                else {
                   var $homeTab = $('<li class="home"><a href="#top" >test</a></li>');
                   $(".main-nav li").css({
                      'position': 'fixed',
                      'width': '100%', 
                      'top':'0', 
                      'left':'0', 
                      'margin-top':'0'
                   });
                   if(!added) {
                      $("#main-nav").prepend($homeTab);
                      added = true; 
                   }
                   $(".thick-line-header").css("display","none");    
                }
             };
             $(window).scroll(top);
          }
       };
       windowWidth();
    });

I hope this can help :)

Answer 2

You're giving a position:fixed on the list items. You need to set the 'fixed' option on the container. e.g.

$(".main-nav").css({'position': 'fixed', 'width': '100%', 'top':'0', 'left':'0', 'margin-top':'0'});

instead of

$(".main-nav li").css({'position': 'fixed', 'width': '100%', 'top':'0', 'left':'0', 'margin-top':'0'});

Hope this helps!