function lazyload(option) {
    var settings = {
defObj: null,
defHeight: 0
    };
    settings = $.extend(settings, option || {});
    var defHeight = settings.defHeight;
    var defObj = (typeof settings.defObj == "object") ? settings.defObj.find("img") : $(settings.defObj).find("img");
    var pageTop = function() {
return document.documentElement.clientHeight + Math.max(document.documentElement.scrollTop, document.body.scrollTop) - settings.defHeight;
    };
    var imgLoad = function() {
defObj.each(function() {
    if ($(this).offset().top <= pageTop()) {
        var src2 = $(this).attr("src2");
//已顯示的不用再顯示
if (src2) {
                    //顯示后，去掉src2屬性
    $(this).attr("src", src2).removeAttr("src2");
}
            }
});
    };
    imgLoad();
    $(window).bind("scroll", function() {
        imgLoad();
    });
}
lazyload({
    defObj:".w1"
});