Append HTML list items to another list using jQuery

append.js

var $window = $(window);
  
function checkWidth() {
  
    // get window size
    var windowsize = $window.width();
  
    // Move top menu items into parent menu
    if (windowsize <= 991) {
  
        if( $('.parent-menu ul').has('li.from-top-nav').length == 0) { 
          
            var top_nav = $('.top-menu ul li').clone();
            var count = top_nav.lenth;

            top_nav.each(function(i) {
                var new_top_nav = $(this).addClass("from-top-nav");
                var main_nav = $('.parent-menu ul');
            });
          
            top_nav.appendTo('.parent-menu ul');
       
        } 
      
        $('span.search-text').remove();

    } else if (windowsize => 992) {
      
        // Destroy from-top-nav items and reverse the process 
        $('.parent-menu ul li.from-top-nav').remove();
                
        // Append "search" text to search icon on mobile
        var search_text = $( "<span class='search-text' style='font-weight:500;'>Search</span>" );
      
        // only append if it doesn't exist
        if ( $('span.search-text').length === 0 ) {
            $('.search-icon').append(search_text).css('font-weight', '500'); 
        }
      
    } 
   
}

// Execute on load
checkWidth();

// Bind event listener
$(window).resize(checkWidth);