JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<button class="add">ADD</button>
<ul class="item">
  <li class="abc">123</li>
  <li class="pp">12</li>
  <li class="abc">78</li>
  <li class="ac">13</li>
</ul>

<ul class="newItems"></ul>

JavaScript

$('.add').click(function () {
   var $items = $('.item li');
   var $newItem =$items.map(function (i,item) {
     console.log($(item).text());
     return parseInt($(item).text()) +10;
   }).get();
   
   $.each($newItem, function(i, item){
    $(".newItems").append("<li>"+item+"</li>");
   });
   
 });