JSFiddle - React, Tailwind, and code Playground

HTML

<div id="resize">
<div id="drag">
</div>
</div>

CSS

#resize {
  position: fixed;
  right: 30px;
  left: calc(100% - 120px);
  height: 90px;
  width: 90px;
  background-color: blue;
  resize: both;
  overflow: auto;
}

#drag {
  background-color:red;
  height: 20px;
}

JavaScript

dragElement(document.getElementById("resize"));

function dragElement(elmnt) {
    var pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;
    if (document.getElementById("drag")) {
        document.getElementById("drag").onmousedown = dragMouseDown;
    } else {
        elmnt.onmousedown = dragMouseDown;
    }
    
function dragMouseDown(e) {
        e = e || window.event;
        e.preventDefault();
        pos3 = e.clientX;
        pos4 = e.clientY;
        document.onmouseup = closeDragElement;
        document.onmousemove = elementDrag;
}

    function elementDrag(e) {
        e = e || window.event;
        e.preventDefault();
        pos1 = pos3 - e.clientX;
        pos2 = pos4 - e.clientY;
        pos3 = e.clientX;
        pos4 = e.clientY;
        elmnt.style.top = (elmnt.offsetTop - pos2) + "px";
        elmnt.style.left = (elmnt.offsetLeft - pos1) + "px";
    }

    function closeDragElement() {
        document.onmouseup = null;
        document.onmousemove = null;
    }
}