首先需要获取屏幕大小：
var screenWidth = document.documentElement.clientWidth;
var screenHeight = document.documentElement.clientHeight;
接着可以定义动画（星星透明度）：
@keyframes flash {
0%{opacity: 0}
25%{opacity: 0.25}
50%{opacity: 0.5}
75%{opacity: 0.75}
100%{opacity: 1}
}
全部代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
div{
width: 70px;
height: 80px;
background: url("./images/star.jpg") no-repeat;
animation: flash 1s;
}
body{
background-color: black
}
@keyframes flash {
0%{opacity: 0}
25%{opacity: 0.25}
50%{opacity: 0.5}
75%{opacity: 0.75}
100%{opacity: 1}
}
</style>
</head>
<body>
<script>
var screenWidth = document.documentElement.clientWidth;
var screenHeight = document.documentElement.clientHeight;
// 生产50个星星
for (let i = 0; i <50 ; i++) {
var box=document.createElement('div');
document.body.appendChild(box);
x=Math.random()*screenWidth;
y=Math.random()*screenHeight;
box.style.position='relative';
box.style.left=x+'px';
box.style.right=y+'px';
}
boxList=document.getElementsByTagName("div");
for (let i = 0; i < boxList.length; i++) {
boxList[i].onmouseover=function () {
this.style.transform='scale(1.5,1.5)';
};
boxList[i].onmouseout=function () {
this.style.transform='scale(1,1)';
};
}
</script>
</body>
</html>
效果如下：
