JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Glow Cursor</title>
</head>
<body>
<div class="box"></div>

</body>
</html>

CSS

.box {
  width: 300px;
  height: 300px;
  border: 2px solid blue;
}

JavaScript

var box = document.querySelector('.box');

box.addEventListener('mousemove', function (e) {
  var rect = e.target.getBoundingClientRect();
  var x = e.clientX - rect.left;
  var y = e.clientY - rect.top;
  
  box.style.background = `radial-gradient(circle at ${x}px ${y}px, rgba(138, 189, 61, 1) 0%, rgba(255, 255, 255, 1) 150px`;
});

box.addEventListener('mouseleave', function () {
  box.style.background = null;
});