JSFiddle - React, Tailwind, and code Playground

HTML

<div id="prCol1">
..content....content....content....content....content....content..
..content....content....content....content....content....content..
..content....content....content....content....content....content..
</div>

<div id="prCol2" class="slideshow">
    ..content..
</div>

CSS

div {
    border: 1px solid #ccc;
}

JavaScript

window.onload = fixHeight();

function fixHeight() {
    var divh = document.getElementById('prCol1').offsetHeight;
    document.getElementById('prCol1').innerHTML = '<ul><li>' + divh + '</li></ul>';
    document.getElementById('prCol2').style.height = divh + 'px';
}