JSFiddle - React, Tailwind, and code Playground

HTML

<div id="nav"></div>

CSS

#nav {    
    width:100px;
    height:100px;
    background:grey;
    color:#fff;
}

JavaScript

window.onresize = function(e){
    var str = 'ширина окна '+window.innerWidth + 
        ' высота окна '+window.innerHeight;
    var div  = document.getElementById("nav");
    div.style.height = window.innerHeight + "px";
    div.style.width = window.innerWidth + "px";
    div.innerHTML = str;

}