JSFiddle - React, Tailwind, and code Playground

HTML

<div class="draggable"></div>
<div id="droppable"></div>
<div id="block"></div>

CSS

#droppable {
    border: 1px solid black;
    background-color: green;
    position: absolute;
    top: 100px;
    left: 200px;
    height: 300px;
    width: 300px;
}
.draggable {
    border: 1px solid black;
    background-color: blue;
    position: absolute;
    top: 10px;
    left: 30px;
    height: 30px;
    width: 30px;
    z-index: 20;
}
#block {
    border: 1px solid black;
    background-color: red;
    position: absolute;
    top: 200px;
    height: 100px;
    width: 100%;
    z-index: 10;
}

JavaScript

$('.draggable').draggable({
    revert: 'invalid'
});

$('#droppable').droppable({
    accept: '.draggable',
    drop: function (e, ui) {
        ui.draggable.hide();
        console.log(ui);
        var target = document.elementFromPoint(ui.offset.left, ui.offset.top);
        if (!target || target.id != "droppable") ui.draggable.draggable({
            revert: true
        });
        else  ui.draggable.draggable({
            revert: false
        });
        ui.draggable.show();
        }
    });