JSFiddle - React, Tailwind, and code Playground

HTML

<svg version="1.0" width="100" height="100" viewbox="0 0 100 100">
    <rect x="0" y="0" width="100" height="100" fillStyle="black"/>
</svg>

<div><span id="x"></span>/<span id="y"></span></div>
<div id="dims"></div>

JavaScript

var x = document.getElementById("x"),
    y = document.getElementById("y"),
    dims = document.getElementById("dims"),
    rect = document.querySelector("svg rect");

rect.addEventListener("mousemove", function(evt) {
    dims.innerHTML = JSON.stringify(evt.target.getBoundingClientRect());
    x.innerHTML = evt.offsetX;
    y.innerHTML = evt.offsetY;
}, false);