JSFiddle - React, Tailwind, and code Playground

HTML

<li data-for-something="1"></li>
<li data-for-something="1"></li>
<li data-for-something="2"></li>
<li data-for-something="3"></li>
<li data-for-something="4"></li>

JavaScript

var array = new Array;

$('li').each( function() { 
    array.push(parseInt($(this)[0].dataset.forSomething));
});

console.log(Math.max.apply(Math, array));