JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="new-item" />
    <input type="button" value="Adicionar" id="add-item" />
    
    <ul>
        <li>Item 1</li>
        <li>Item 2</li>
        <li>Item 3</li>
    </ul>

JavaScript

$(function() {
        $('#add-item').on('click', function() {
            var itemText = $('#new-item').val();
            
            var newEl = $('<li>' + itemText + '</li>');
            newEl.hide();
            
            $('ul').prepend(newEl);
            
            newEl.slideDown();
            
        });
    });