怎么实现的呢，哈哈哈，代码看这里：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>梦幻登录</title>
<style type="text/css">
* {
margin: 0;
padding: 0;
list-style: none;
}
body {
overflow: hidden;
}
#bg_wrap {
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
overflow: hidden;
}
#bg_wrap div {
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
opacity: 0;
/* 设置透明度 */
transition: opacity 3s;
}
/* nth-of-type(1) *筛选选择器选择第一个*/
#bg_wrap div:nth-of-type(1) {
opacity: 1;
}
#Login {
width: 272px;
height: 300px;
margin: 200px auto;
}
#Login .move {
position: absolute;
top: -100px;
z-index: 999;
}
#Login h3 {
width: 270px;
font-size: 30px;
font-weight: 700;
color: #fff;
font-family: '微软雅黑';
text-align: center;
margin-bottom: 30px;
cursor: move;
/* top: 100px; */
}
/* #username {
top: 170px;
}
#password {
top: 225px;
} */
#Login input.text {
width: 270px;
height: 42px;
color: #fff;
background: rgba(45, 45, 45, 0.15);
border-radius: 6px;
border: 1px solid rgba(255, 255, 255, 0.15);
box-shadow: 0 2px 3px 0 rgba(0, 0, 0, 1.0) inset;
text-indent: 10px;
}
#Login input.btn {
/* top: 280px; */
background: #ef4300;
width: 272px;
height: 44px;
border-radius: 6px;
color: #fff;
box-shadow: 0 15px 30px 0 rgba(255, 255, 255, 0.25) inset, 0 2px 7px 0 rgba(0, 0, 0, 0.2);
/* -webkit-box-shadow: 0 15px 30px 0 rgba(255, 255, 255, 0.25) inset, 0 2px 7px 0 rgba(0, 0, 0, 0.2);
-moz-box-shadow: 0 15px 30px 0 rgba(255, 255, 255, 0.25) inset, 0 2px 7px 0 rgba(0, 0, 0, 0.2); */
border: 0;
text-align: center;
}
/* #Login input.focus {
outline: none;
box-shadow: 0 2px 3px 0 rgba(0, 0, 0, 0.2) inset;
} */
input::-webkit-input-placeholder {
color: #fff;
}
</style>
</head>
<body>
<div id="bg_wrap">
<div><img src="images/1.jpg" width="100%" height="100%"></div>
<div><img src="images/2.jpg" width="100%" height="100%"></div>
<div><img src="images/3.jpg" width="100%" height="100%"></div>
</div>
<div id="Login">
<h3 id="title" class="move">User Login</h3>
<form action="#" method="post" target="_blank">
<input type="text" placeholder="UserName" name="username" id="username" class="text move">
<input type="password" placeholder="PassWord" name="password" id="password" class="text move">
<input type="submit" value="Sign in" class="btn move" id="submit">
</form>
</div>
<script type="text/javascript">
/*背景渐变*/
/*function(){} 匿名函数
()() IIFE匿名函数立刻执行，函数自执行体*/
(function() {
var timer = null; //声明定时器
var oImg = document.querySelectorAll('#bg_wrap div') //h5最新元素获取写法获取到的是一组元素
//querySelector获取单个元素的 兼容ie8
var len = oImg.length; //3
var index = 0;
timer = setInterval(function() {
oImg[index].style.opacity = 0;
index++;
// if(index>=3){
// index=0;
// }
index %= len; //index=index%len求模取余 0%3=0; 1%3=1; 2%3=2; 3%3=0;
oImg[index].style.opacity = 1;
}, 2000);
})();
// 重力模拟弹跳系统
(function() {
/*
改变定位元素的top值
达到指定位置之后进行弹跳一次
多个元素一次运动
动画序列*/
var oMove = document.querySelectorAll('.move');
var oLen = oMove.length;
var timer = null;
var timeout = null;
var speed = 3; //移动距离
move(oLen - 1);
function move(index) {
if (index < 0) {
clearInterval(timer); //清除循环定时器
clearTimeout(timeout); //清除延时定时器
return; //终止函数
}
var endTop = 150 + (index * 60); //根据下标计算endTop值
timer = setInterval(function() {
speed += 3;
var T = oMove[index].offsetTop + speed; //设置每一次的top值
if (T > endTop) {
T = endTop;
speed *= -1 //取反，让移动距离变为负数
speed *= 0.4;
//慢慢停下来
}
oMove[index].style.top = T + 'px';
}, 20);
timeout = setTimeout(function() {
clearInterval(timer);
index--;
console.log(9);
move(index);
console.log(index);
}, 900) //过900毫秒之后再执行方法里的代码
}
})()
</script>
</body>
</html>
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