JSFiddle - React, Tailwind, and code Playground

HTML

<body onload="aviso()">
    
    <div id="divRojo">
        Div Rojo 
    </div>
    
</body>

CSS

#divRojo {
    width:100px;
    height:100px;
    background:red;
    left:200px;
    top:200px;
    position:absolute;
}

JavaScript

function aviso(){    
    var el = document.getElementById("divRojo");
    var st = getComputedStyle(el);
    console.log("top: "+ st.top);         
    console.log("position: "+st.position);   

    alert("Top: " + st.top + ", Position: " + st.position);
}