图片的预加载和按需加载

图片预加载

<!DOCTYPE HTML>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>无标题文档</title>

<style>

    img{width:500px;margin:100px auto;display: block;}

</style>

<script>

window.onload = function() {

    var iCur = 0;

    var i = 0;

    var oImg = document.getElementById('img1');



    var arr = [

            [

                'http://b.hiphotos.baidu.com/image/pic/item/e4dde71190ef76c666af095f9e16fdfaaf516741.jpg',

                'http://g.hiphotos.baidu.com/image/pic/item/4a36acaf2edda3ccd2994a5402e93901213f9241.jpg',

                'http://a.hiphotos.baidu.com/image/pic/item/2fdda3cc7cd98d10b1a9fe45223fb80e7bec9041.jpg',

                'http://e.hiphotos.baidu.com/image/pic/item/96dda144ad34598216d017e60ff431adcbef8468.jpg',

                'http://d.hiphotos.baidu.com/image/pic/item/7c1ed21b0ef41bd5a6e81a8052da81cb39db3d0e.jpg',

                'http://b.hiphotos.baidu.com/image/pic/item/14ce36d3d539b600ab94fdc3ea50352ac65cb768.jpg',

                'http://c.hiphotos.baidu.com/image/pic/item/cf1b9d16fdfaaf5179eeb78f8f5494eef01f7af4.jpg',

                'http://d.hiphotos.baidu.com/image/pic/item/8cb1cb13495409234610554e9158d109b3de4980.jpg',

                'http://d.hiphotos.baidu.com/image/pic/item/5ab5c9ea15ce36d386b6b50039f33a87e950b14b.jpg',

                'http://b.hiphotos.baidu.com/image/w%3D230/sign=84a0b54d93ef76c6d0d2fc28ad17fdf6/fc1f4134970a304e4462c796d2c8a786c9175c1d.jpg'],[

                '01',

                '02',

                '03',

                '04',

                '05',

                '06',

                '07',

                '08',

                '09',

                '10'

            ]

    ]

;

    

    



    oImg.onclick = function() {

        i++;

        if (i < arr[0].length) {

            oImg.src = arr[0][i];

        }

    }



    preLoadImg();

    function preLoadImg() {

        var oImage = new Image();

        oImage.src = arr[0][iCur];



        oImage.onload = oImage.onerror = function() {

            iCur++;

            if (iCur < arr[0].length) {

                preLoadImg();    //递归

            }

            document.title = iCur + ' / ' + arr[0].length;

        }

    }

    

}

</script>

</head>



<body>

    <img src="http://bizhi.zhuoku.com/2014/10/01/zhuoku/zhuoku001.jpg" alt="1111" id="img1"/>

</body>

</html>

图片按需加载

<!DOCTYPE HTML>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>无标题文档</title>

<style>

#ul1 {margin: 100px auto 0; padding: 0;}

li {float: left; margin:0 0 10px 10px; list-style:none; border: 1px solid black;}

img {width: 290px; height: 200px; display: block;}

</style>

<script>

window.onload = function() {

    

    var oUl = document.getElementById('ul1');

    var aImg = oUl.getElementsByTagName('img');

    

    showImage();

    

    window.onscroll = showImage();

    

    function showImage() {

        

        var scrollTop  = document.documentElement.scrollTop || document.body.scrollTop;

        

        for (var i=0; i<aImg.length; i++) {

            

            if ( !aImg[i].isLoad && getTop(aImg[i]) < scrollTop + document.documentElement.clientHeight ) {

                //alert(i);

                aImg[i].src = aImg[i].getAttribute('_src');

                aImg[i].isLoad = true;

            }

            

        }

        

    }

    

    function getTop(obj) {

        var iTop = 0;

        while(obj) {

            iTop += obj.offsetTop;

            obj = obj.offsetParent;

        }

        return iTop;

    }

    

}

</script>

</head>



<body>

    <ul id="ul1">

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/1.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/2.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/3.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/4.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/5.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/6.jpg" src="img/white.JPG" /></li>

        <li><img _src="img/7.jpg" src="img/white.JPG" /></li>

    </ul>

</body>

</html>

 

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