JSFiddle - React, Tailwind, and code Playground

HTML

<aside draggable="true" id="dragme">
    Drag Me
</aside>

<aside droppable="true" id="drophere">
    Drop Here
</aside>

<div id="notes">
    Notes:
    <ul>
        <li>drag: In Chrome the x/y values for drag are reasonable as the drag is happening, 
            but then you get some crazy values in the last drag event when
            the element is dropped.</li>
        <li>drag: In Firefox, there are no x/y values in drag events at all</li>
        <li>drag: In Safari, the x/y values in drag events seem reasonable</li>
        <li>dragend: In Chrome, the x/y values in dragend are just strange.  The screenX/screenY values seem to be almost accurate, except they are offset by the distance from the bottom left corner of the dragged element to the place where the dragged element was grabbed.</li>
        <li>dragend: In Safari, the x/y values in the dragend seem to all be relevant to the outer window, not the iframe (which exists since this is inside jsFiddle.  This is different from the dragstart event, which sets all the x/y values (except for screenX/screenY) relative to the iframe</li>
        <li>dragend: In Firefox, there is only screenX/y, and it seems right.</li>
        <li>dragenter/dragover/dragleave/drop: Seem good in Chrome/Safari/FireFox except that FireFox does not have offsetX/Y values</li>
    </ul>
</div>

<table>
    <tr>
        <th></th>
        <th>clientX/Y</th>
        <th>pageX/Y</th>
        <th>screenX/Y</th>
        <th>offsetX/Y</th>
    </tr>
    <tr>
        <th>dragstart</th>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <th>drag</th>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <th>dragend</th>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <th></th>
        <td colspan=4 style="height: 3px; background-color: grey"></td>
    </tr>
    <tr>
        <th>dragenter</th>
       ...

CSS

body {
    height: 400px;
}

ul {
    list-style-type: circle;
}

aside { 
    position:  absolute;
    left: 0;
    top: 0; /* set these so Chrome doesn't return 'auto' from getComputedStyle */
    width: 80px; 
    height: 20px;
    background: rgba(255,255,255,0.66); 
    border: 2px  solid rgba(0,0,0,0.5); 
    border-radius: 4px; padding: 8px;
}

aside#dragme {
    top: 0px;
    left: 0px
}

aside#drophere {
    top: 100px;
    left: 100px
}

div#notes {
    position: absolute;
    top: 200px;
    left: 300px;
}

table {
    position: absolute;
    top: 0px;
    left: 300px;
    border-collapse: collapse;
}

th {
    font-weight: bold;
    padding: 0px 3px;
}

td {
    border: 1px solid grey;
}

JavaScript

function setCell(eventType, label, x, y) {
    var row = ['', 'dragstart', 'drag', 'dragend', '', 
               'dragenter', 'dragover', 'dragleave', 
               'drop'].indexOf(eventType);
    var cell = ['', 'client', 'page', 'screen', 'offset'].indexOf(label);
    var val = [x, y].join('/');
    document.getElementsByTagName('table')[0].rows[row].cells[cell].textContent = val; 
}

function setRow(evt) {
    var eventType = evt.type;
    setCell(eventType, 'client', evt.clientX, evt.clientY);
    setCell(eventType, 'page', evt.pageX, evt.pageY);
    setCell(eventType, 'screen', evt.screenX, evt.screenY);
    setCell(eventType, 'offset', evt.offsetX, evt.offsetY);
}

function dragstart(evt){
    // FF needs this
    evt.dataTransfer.setData("text/plain", "asd");
    setRow(evt);
}

function dragover(evt){
    evt.preventDefault();
    if (evt.stopPropagation) evt.stopPropagation();
    setRow(evt);
}

function drop(evt) {
    console.log(evt.stopPropagation);
    if(evt.preventDefault) evt.preventDefault();
    if (evt.stopPropagation) evt.stopPropagation();
    setRow(evt);
}


var dragme = document.getElementById('dragme'); 
dragme.addEventListener('dragstart',dragstart,false); 
dragme.addEventListener('drag',setRow,false); 
dragme.addEventListener('dragend',setRow,false); 
drophere.addEventListener('dragenter',setRow,false); 
drophere.addEventListener('dragover',dragover,false); 
drophere.addEventListener('dragleave',setRow,false); 
drophere.addEventListener('drop',drop,false);