这个一般用于会员登录页面。刷新一次变一次背景大图，代码如下
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
html{
height: 100%;
}
body {
background-size: 100% 100%;
background-repeat: no-repeat;
height: 100%;
}
</style>
</head>
<body>
</body>
<script>
let imgArr = ["https://iknow-base.cdn.bcebos.com/qixiqbpcbanner.jpg", "https://iknow-base.cdn.bcebos.com/%E9%BB%84%E5%9C%A3%E4%BE%9D%E7%89%A9%E6%96%99%2Fqb%E9%A1%B5%E8%BD%AE%E6%92%AD%E5%9B%BE%E9%BB%84%E5%9C%A3%E4%BE%9D270x170x2.jpg", "https://iknow-base.cdn.bcebos.com/trishafish%2F%E7%9F%A5%E9%81%93PC-QB-540-280.jpg"]; //图片数据
let num = 0;
let setNum = localStorage.getItem("num");
if (setNum) {
num = setNum
}
console.log(imgArr[num]); //日志
document.body.style.backgroundImage = "url(" + imgArr[num] + ")"
if (num == imgArr.length - 1) {
num = 0;
} else {
num++;
}
localStorage.setItem("num", num)
</script>
</html>
