JS延迟加载图片
图片延迟加载的JS代码。将页面的img标签中的src写成src2即可使用。
例如：

<img alt="lazy image" title="lazy image" src2="http://www.abc.com/lazeimage.jpg">

JS源代码如下(需要用到jquery):

function getPosition(h) {
    var a = navigator.userAgent.toLowerCase();
    var b = (a.indexOf("opera") != -1);
    var e = (a.indexOf("msie") != -1 && !b);
    var d = h;
    if (d.parentNode === null || d.style.display == "none") {
        return false
    }
    var l = null;
    var k = [ ];
    var i;
    if (d.getBoundingClientRect) {
        i = d.getBoundingClientRect();
        if (a.indexOf("ipad") != -1) {
            return {
                x: i.left,
                y: i.top
            }
        }
        var c = jQuery(window).scrollTop();
        var f = jQuery(window).scrollLeft();
        return {
            x: i.left + f,
            y: i.top + c
        }
    } else {
        if (document.getBoxObjectFor) {
            i = document.getBoxObjectFor(d);
            var j = (d.style.borderLeftWidth) ? parseInt(d.style.borderLeftWidth) : 0;
            var g = (d.style.borderTopWidth) ? parseInt(d.style.borderTopWidth) : 0;
            k = [i.x - j, i.y - g]
        } else {
            k = [d.offsetLeft, d.offsetTop];
            l = d.offsetParent;
            if (l != d) {
                while (l) {
                    k[0] += l.offsetLeft;
                    k[1] += l.offsetTop;
                    l = l.offsetParent
                }
            }
            if (a.indexOf("opera") != -1 || (a.indexOf("safari") != -1 && d.style.position == "absolute")) {
                k[0] -= document.body.offsetLeft;
                k[1] -= document.body.offsetTop
            }
        }
    }
    if (d.parentNode) {
        l = d.parentNode
    } else {
        l = null
    }
    while (l && l.tagName != "BODY" && l.tagName != "HTML") {
        k[0] -= l.scrollLeft;
        k[1] -= l.scrollTop;
        if (l.parentNode) {
            l = l.parentNode
        } else {
            l = null
        }
    }
    return {
        x: k[0],
        y: k[1]
    }
}
jQuery(document).ready(function lazyload() {
    var d = jQuery("img[src2]");
    var a = function() {
        return jQuery(window).height() + jQuery(window).scrollTop()
    };
    imgLoad(d, a());
    var c = 150;
    var b = 0;
    jQuery(window).bind("scroll",
    function() {
        var e = Math.abs(jQuery(window).scrollTop() - b);
        if (e >= c) {
            imgLoad(d, a());
            if (imgLoadStatus == 1) {
                b += c;
                imgLoadStatus = 0
            }
        }
    })
});
var imgLoadStatus = 0;
function imgLoad(b, a) {
    b = jQuery("img[src2]");
    b.each(function() {
        var d = jQuery(this).attr("src2");
        if (d) {
            var c = getPosition(jQuery(this)[0]).y;
            if (c <= a && (c + jQuery(this).height()) >= jQuery(window).scrollTop()) {
                jQuery(this).attr("src", d).removeAttr("src2")
            }
        }
    });
    imgLoadStatus = 1
};