JSFiddle - React, Tailwind, and code Playground

HTML

<div contenteditable></div>

CSS

* {
    margin: 0;
    padding: 0;
}
div[contenteditable] {
    position: absolute;
    left: 50%;
    top: 50%;
    margin-left: -160px;
    margin-top: -20px;
    width: 300px;
    min-height: 20px;
    line-height: 20px;
    padding: 10px;
    //box-shadow: 0 0 0 1px #ddd;
}

JavaScript

var $div = $('div[contenteditable]');
var divPadding = parseInt($div.css('padding-top'));
var divLineHeight = parseInt($div.css('line-height'));

var centerDiv = function () {
    var windowHeight = window.innerHeight;
    var divHeight = $div.height();
    var divLines = divHeight / divLineHeight;

    var divTop = (windowHeight / 2) - ((divLines - 1) * divLineHeight) - divPadding;

    $div.css('top', divTop);
}

setInterval(function () {
    centerDiv();
}, 50);