JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div-a">
			<div class="babydiv" onmousedown="divMove();">
			
			
			</div>
		</div>
		
		<a onclick="adddiv()">add div</a>

CSS

* {
	padding: 0;
	margin: 0;
}

#div-a {
	position: relative;
	width: 300px;
	height: 300px;
	background-color: red;
}

.babydiv {
	transform: translate(-50%, -50%);
	position: relative;
	width: 300px;
	height: 200px;
	background-color: blue;
}

JavaScript

var diva = document.getElementById("div-a");

function adddiv() {
	var newdiv = document.createElement("div");
	newdiv.className = "babydiv";
	
	diva.appendChild(newdiv);
}


function divMove(e){
  	divb.style.top = e.clientY + 'px';
  	divb.style.left = e.clientX  + 'px';
}