无缝轮播是一个很常见的效果，理解逻辑之后就很简单了。
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>做无缝轮播</title>
<script src="js/jquery-3.4.1.min.js"></script>
<style>
* {
margin: 0;
padding: 0;
user-select: none;
}
#div {
border: 1px solid lightgray;
width: 600px;
height: 300px;
margin: 20px;
overflow: hidden;
}
.item {
border: 1px solid lightgray;
width: 96%;
height: 50px;
margin: 10px auto;
}
</style>
</head>
<body>
<div id="div">
<div class="rollbox"></div>
</div>
</body>
</html>
<script>
$(document).ready(function() {
for (var i = 0; i < 7; i++) {
var $item = $("<div class='item'>" + i+ "</div>");
$item.appendTo($("#div .rollbox"));
}
})
//轮播动作
$(function() {
$("#div").roll(1);
})
$.prototype.roll = function(span) {
span = span == undefined ? 20 : span; //滚动速率
var $that = $(this).find('.rollbox');
var index = 0;
var t = setInterval(function() {
$that.css('margin-top', index + 'px');
index--;
check();
}, span)
//
$that.mouseenter(function() {
clearInterval(t);
})
$that.mouseleave(function() {
t = setInterval(function() {
$that.css('margin-top', index + 'px');
index--;
check();
}, span)
})
function check(){
var first = $that.children().first();
var top = parseInt(first.css('margin-top').replace('px',''));
var bottom = parseInt(first.css('margin-bottom').replace('px',''));
var height =first.height();
bw = parseInt(first.css('border-width').replace('px',''));
var temp = index+top+height+bottom;
if(temp==top-2*bw){
var last = $that.children().last();
last.after(first);
$that.css('margin-top','0px');
index=0;
}
}
}
</script>
