JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
</ul>

JavaScript

var secundario = [];

$('ul li').each(function(i){
    if (i % 2 != 0) return;
    var removido = $(this).remove();
    secundario.push(removido);
});
$('ul').append(secundario);