JSFiddle - React, Tailwind, and code Playground

HTML

<div class="square"></div>

CSS

html, body {
    margin: 0;
    height: 100%;
}
.square {
    width: 300px;
    height: 300px;
    margin: 0 auto;
    background-color: #7ad;
    -moz-transform-origin: center top;
      -o-transform-origin: center top;
}

JavaScript

function zoomSquare() {
    var $square = $('.square');

    var viewportHeight = $(window).height();
    var squareHeight = $square.height();
    var desiredHeight = Math.round(viewportHeight * 0.95);
    var zoom = (desiredHeight / squareHeight);

    $square.css('zoom', zoom);
    $square.css('-moz-transform', 'scale(' + zoom + ')');
    $square.css(  '-o-transform', 'scale(' + zoom + ')');
}

// When the browser is resized
$(window).on('resize', function(){ zoomSquare(); });

// When the page first loads
$(document).ready(function(){
    zoomSquare();
});