JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="effects-list" class="effects-list">
    <li data-creative="5">Creative</li>
</ul>

JavaScript

var effectData = document.getElementById("effects-list").getElementsByTagName("li");

//I also tried the below method: 
// var effectData = $('.effects-list li');


var creative = effectData.getAttribute('data-creative');
alert(creative);