JSFiddle - React, Tailwind, and code Playground

HTML

<div id="res"> 
      <li class="new" id="10">Novo Elemento</li> 
          <li class="new" id="20">Novo Elemento</li> 
          <li class="new" id="30">Novo Elemento</li> 
   </div>

JavaScript

var res = document.getElementById('res');
res.addEventListener('click', function(e){
       var elemento = e.target;
       if (elemento.tagName.toLowerCase() == 'li' && elemento.classList.contains('new')) alert(elemento.id);
       else return false;
}, false);