<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document
</title>
<style>
div {
position: absolute;
width: 30px;
height: 30px;
background-color: green;
display: none;
}
</style>
</head>
<body>
<div></div>
<script>
var d = document.querySelector('div');
document.addEventListener('mouseover', function () {
d.style.display = 'block';
});
document.addEventListener('mouseout', function () {
d.style.display = 'none';
});
document.addEventListener('mousemove', function (e) {
d.style.left = e.pageX - 15 + 'px';
d.style.top = e.pageY - 15 + 'px';
});
</script>
</body>
</html>
主要思想，根据鼠标的坐标改变div的left,top值
