<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>图片懒加载(可视区域加载)</title>
<style>
* {
padding: 0px;
margin: 0px;
}
html,
body {
100%;
min-height: 100%;
}
#SB {
margin: 0;
padding: 0;
list-style: none;
}
#SB .in {
border: 1px solid red;
margin: 10px;
text-align: center;
height: 400px;
400px;
float: left;
}
.in img {
border: none;
vertical-align: middle;
height: 400px;
400px;
}
</style>
</head>
<body>
<ul id="SB">
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
<li class="in"><img src="" data-imgurl="img/show.jpg" alt="loading"></li>
</ul>
<script type="text/javascript">
var aImages = document.getElementById("SB").getElementsByTagName('img'); //获取id为SB的文档内所有的图片
loadImg(aImages);
window.onscroll = function() { //滚动条滚动触发
loadImg(aImages);
};
//getBoundingClientRect 是图片懒加载的核心
function loadImg(arr) {
for(var i = 0, len = arr.length; i < len; i++) {
if(arr[i].getBoundingClientRect().top < document.documentElement.clientHeight && !arr[i].isLoad) {
arr[i].isLoad = true; //图片显示标志位
//arr[i].style.cssText = "opacity: 0;";
(function(i) {
setTimeout(function() {
if(arr[i].dataset) { //兼容不支持data的浏览器
aftLoadImg(arr[i], arr[i].dataset.imgurl);
} else {
aftLoadImg(arr[i], arr[i].getAttribute("data-imgurl"));
}
arr[i].style.cssText = "transition: 1s; opacity: 1;" //相当于fadein
}, 500)
})(i);
}
}
}
function aftLoadImg(obj, url) {
var oImg = new Image();
oImg.onload = function() {
obj.src = oImg.src; //下载完成后将该图片赋给目标obj目标对象
}
oImg.src = url; //oImg对象先下载该图像
}
</script>
</body>
</html>