JSFiddle - React, Tailwind, and code Playground

HTML

<div id="row1">Some content</div>
<div id="row2">Some content</div>
<div id="row3">Some content</div>
<div id="row5656">Some content</div>
<div id="row7">Some content</div>
<div id="row15">Some content</div>
<div id="row915">Some content</div>
<div id="row919">Some content</div>
<input type="button" id="btnTest" value="LastID"/>

JavaScript

$('#btnTest').live("click", function() {
    alert($('div:last').attr('id').split('row')[1]);
 });