JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="grow">Testing</div>
</div>

CSS

.parent {
    height: 500px;
    background: red;
}

.grow {
    background-color: blue;
}

JavaScript

$(document).ready(function() {

    $(window).resize(function() {
        $('.grow').css({
            height: $('.parent').height()-50,
            backgroundPosition: '50px ' + ($('.parent').height()-50) + 'px'
        });
    });

});