JSFiddle - React, Tailwind, and code Playground

HTML

<div id=box>
    <div id=item1>Item 1</div>
    <div id=item2><br>Item 2</div>
</div>
<button type=button>apply align-items: flex-end</button>

CSS

body {
    font-size: 20px;
}
#box {
    display: -webkit-flex;
}

JavaScript

document.querySelector('button').onclick = function () {
    document.querySelector('#box').style.webkitAlignItems = 'flex-end'
}