图片延迟加载

<script src="js/jquery-1.7.2.min.js" type="text/javascript"></script>
        <script type="text/javascript">
            (function ($) {
                $.extend($.fn, {

                    lazyloadImg: function (option) {
                        var settings = { defObj: null, defHeight: 0 };
                        settings = $.extend(settings, option || {});
                        var defHeight = settings.defHeight,
                        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 orgSrc = $(this).attr("orgsrc");
                                    if (orgSrc) {
                                        $(this).attr("src", orgSrc).removeAttr("orgsrc");
                                    }
                                }
                            });
                        };
                        imgLoad();
                        var timer = null;
                        $(window).bind("scroll", function () {
                            if (timer) {
                                clearTimeout(timer)
                            }
                            timer = setTimeout(function () { imgLoad(); }, 100);
                        });
                    }

                });
            })(jQuery);
            
            
        </script>
        <script type="text/javascript">
            $(function () {
                $("body").lazyloadImg({ "defObj": "body" });
            });
        </script>