修改jquery.lazyload.js实现页面延迟载入_jquery

jquery.lazyload.js
/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2009 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.5.0
 * 
 * Modify by @cnbaiying
 * Modify time: 2010-12-16
 */
(function($) {

    $.fn.lazyload = function(options) {
        var settings = {
            threshold    : 0,        //阀值
             failurelimit : 0,
            event        : "scroll",
            effect       : "show",
            container    : window
        };
                
        if(options) {
            
            $.extend(settings, options);
        }
        
        /* Fire one scroll event per scroll. Not one scroll event per image. */
        var elements = this;
        
        if ("scroll" == settings.event) {
            $(settings.container).bind("scroll", function(event) {
                var counter = 0;
                elements.each(function() {
      if ($.abovethetop($(this).parent(), settings) || $.leftofbegin($(this).parent(), settings)) {
                            /* Nothing. */
      } else if (!$.belowthefold($(this).parent(), settings) && !$.rightoffold($(this).parent(), settings)) {
                        $(this).trigger("appear");
                    } else {
                        if (counter++ > settings.failurelimit) {
                            return false;
                        }
                    }
                });
                /* Remove image from array so it is not looped next time. */
                var temp = $.grep(elements, function(element) {
                    return !element.loaded;
                });
                elements = $(temp);
            });
        }
        
        this.each(function() {
            var self = this;
            /* When appear is triggered load original image. */
            $(self).one("appear", function() {
                if (!this.loaded) {
                    //alert($(self).parent().html($(self).html()));
                    var tmp_str = $(self).html();
                    tmp_str = tmp_str.replace("&lt;", "<");
                    tmp_str = tmp_str.replace("&gt;", ">");
                    $(self).parent().append(tmp_str);
                    self.loaded = true;
                }
            });

            /* When wanted event is triggered load original image */
            /* by triggering appear.                              */
            if ("scroll" != settings.event) {
                $(self).bind(settings.event, function(event) {
                    if (!self.loaded) {
                        $(self).trigger("appear");
                    }
                });
            }
        });
        
        /* Force initial check if images should appear. */
        $(settings.container).trigger(settings.event);
        
        return this;

    };

    /* Convenience methods in jQuery namespace.           */
    /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

    $.belowthefold = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).height() + $(window).scrollTop();
        } else {
            var fold = $(settings.container).offset().top + $(settings.container).height();
        }
        return fold <= $(element).offset().top - settings.threshold;
    };
    
    $.rightoffold = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).width() + $(window).scrollLeft();
        } else {
            var fold = $(settings.container).offset().left + $(settings.container).width();
        }
        return fold <= $(element).offset().left - settings.threshold;
    };
        
    $.abovethetop = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).scrollTop();
        } else {
            var fold = $(settings.container).offset().top;
        }
        return fold >= $(element).offset().top + settings.threshold  + $(element).height();
    };
    
    $.leftofbegin = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).scrollLeft();
        } else {
            var fold = $(settings.container).offset().left;
        }
        return fold >= $(element).offset().left + settings.threshold + $(element).width();
    };
    /* Custom selectors for your convenience.   */
    /* Use as $("img:below-the-fold").something() */

    $.extend($.expr[&#39;:&#39;], {
        "below-the-fold" : "$.belowthefold(a, {threshold : 0, container: window})",
        "above-the-fold" : "!$.belowthefold(a, {threshold : 0, container: window})",
        "right-of-fold"  : "$.rightoffold(a, {threshold : 0, container: window})",
        "left-of-fold"   : "!$.rightoffold(a, {threshold : 0, container: window})"
    });
    
})(jQuery);

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" /> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<meta name="keywords" content="汽车图片,汽车图片壁纸, 汽车图片桌面, 汽车图片库,汽车图片大全" /> 
<meta name="description" content="汽车图片，网上车市汽车图片大全频道为网友提供各种汽车图片及美女图片下载
，各种车型汽车图片桌面，汽车图片壁纸，车展美女图片，美女车模图片等。精彩图片，尽在网上车市。" /> 
<title>【汽车图片|汽车美女图片-汽车图片大全】-网上车市</title> 
<style> 
.switch_textarea {display:none;} 
.div_style {width:600px; height:400px; } 
</style> 
<script type="text/javascript" src="jquery.1.4.4.js"></script> 
<script type="text/javascript" src="lazyload.jquery.js"></script> 
<script> 
$().ready(function(){ 
$(".switch_textarea").lazyload(); 
}); 
</script> 
</head> 
<body> 
<H2>第1张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd2385fd03.jpg" /></textarea></div> 
<H2>第2张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd2366adec.jpg" /></textarea></div> 
<H2>第3张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd233b8da4.jpg" /></textarea></div> 
<H2>第4张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd231a0fd8.jpg" /></textarea></div> 
<H2>第5张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd22e68f56.jpg" /></textarea></div> 
<H2>第6张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd22c55a5d.jpg" /></textarea></div> 
<H2>第7张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd2278872b.jpg" /></textarea></div> 
<H2>第8张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd224a0f6e.jpg" /></textarea></div> 
<H2>第9张图</H2> 
<div class="div_style"><textarea class="switch_textarea"><img src="4bdfd21fb42bc.jpg" /></textarea></div> 
</body> 
</html>