JSFiddle - React, Tailwind, and code Playground

HTML

<h1>Drag Handle</h1>

<div id="draggable" draggable="true">
    <div id="handle">
    </div>
</div>

CSS

#draggable {
    width: 100px;
    height: 100px;
    border: 1px solid black;
}
#handle {
    width: 0;
    height: 0;
    border-right: 20px solid transparent;
    border-top: 20px solid black;
    cursor: move;
}

JavaScript

var draggable = document.getElementById('draggable');
var handle = document.getElementById('handle');
var target = false;
draggable.onmousedown = function(e) {
    target = e.target;
};
draggable.ondragstart = function(e) {
    if (handle.contains(target)) {
        e.dataTransfer.setData('text/plain', 'handle');
    } else {
        e.preventDefault();
    }
};