[转]LazyLoad.js及scrollLoading.js

本文转自：http://blog.csdn.net/ning109314/article/details/7042829

目前图片延迟加载主要分两大块，一是触发加载（根据滚动条位置加载图片）；二是自动预加载（加载完首屏后n秒后自动加载其他位置的图片）。现在最流行使用的就是LazyLoad.js及scrollLoading.js这两个用Jquery写的小插件。

一、LazyLoad实现：

<script type="text/javascript" src="/js/lazyload/jquery.min.js"></script> < script type="text/javascript" src="/js/lazyload/lazyload.js"></script> < script type="text/javascript"> jQuery(document).ready( function($){ $("img").lazyload({ effect : "fadeIn" }); }); < /script>

网上找到一个更好点的处理方式，以下方式转自http://www.poluoluo.com/jzxy/201110/145261.html：

<script type="text/javascript">

//首先用JQ判断浏览器类型及版本，如果是IE8以下的浏览器就用effect=show，否则就用effect=fadeIn，判断浏览器版本函数如下 function checkbrowse() { var ua = navigator.userAgent.toLowerCase(); var is = (ua.match(/\b(chrome|opera|safari|msie|firefox)\b/) || ['', 'mozilla'])[1]; var r = '(?:' + is + '|version)[\\/: ]([\\d.]+)'; var v = (ua.match(new RegExp(r)) || [])[1]; jQuery.browser.is = is; jQuery.browser.ver = v; return { 'is': jQuery.browser.is, 'ver': jQuery.browser.ver } }

//改造Jquery.LazyLoad.js函数，根据浏览器版本来显示不同的滤镜效果 var public = checkbrowse(); var showeffect = ""; if ((public['is'] == 'msie' && public['ver'] < 8.0)) { showeffect = "show" } else { showeffect = "fadeIn" } jQuery(document).ready(function($) { $("img").lazyload({ placeholder: "http://demo.jb51.net/js/2011/lazyload/Js/lazyload/grey.gif", effect: showeffect, failurelimit: 10 }) }); < /script>

html:

<img    src="/js/lazyload/pixel.gif" original="真实图片路径" />

而LazyLoad只是给你一个延迟加载的假象，每次图片都会加载两次，完全就是一个假象的延迟加载。可以修改LazyLoad文件实现真实延迟加载，本人比较懒，就直接在网上找了一个修改好的，嘿嘿

1. /*
2. * Lazy Load - jQuery plugin for lazy loading images
3. *
4. * Copyright (c) 2007-2009 Mika Tuupola
5. *
6. * Licensed under the MIT license:
7. *   http://www.opensource.org/licenses/mit-license.php
8. *
9. * Project home:
10. *   http://www.appelsiini.net/projects/lazyload
11. *
12. * Version:  1.5.0
13. *
14. */
15. (function ($) {
16. $.fn.lazyload = function (options) {
17. var settings = {
18. threshold: 0,
19. failurelimit: 0,
20. event: "scroll",
21. effect: "show",
22. container: window
23. };
24. if (options) {
25. $.extend(settings, options);
26. }
27. /* Fire one scroll event per scroll. Not one scroll event per image. */
28. var elements = this;
29. if ("scroll" == settings.event) {
30. $(settings.container).bind("scroll", function (event) {
31. var counter = 0;
32. elements.each(function () {
33. if ($.abovethetop(this, settings) ||
34. $.leftofbegin(this, settings)) {
35. /* Nothing. */
36. } else if (!$.belowthefold(this, settings) &&
37. !$.rightoffold(this, settings)) {
38. $(this).trigger("appear");
39. } else {
40. if (counter++ > settings.failurelimit) {
41. return false;
42. }
43. }
44. });
45. /* Remove image from array so it is not looped next time. */
46. var temp = $.grep(elements, function (element) {
47. return !element.loaded;
48. });
49. elements = $(temp);
50. });
51. }
52. this.each(function () {
53. var self = this;
54. //删除的代码

/*
* 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
*
*/
(function ($) {
    $.fn.lazyload = function (options) {
        var settings = {
            threshold: 0,
            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, settings) ||
$.leftofbegin(this, settings)) {
                        /* Nothing. */
                    } else if (!$.belowthefold(this, settings) &&
!$.rightoffold(this, 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;
            //删除的代码

1. /* When appear is triggered load original image. */
2. $(self).one("appear", function () {
3. if (!this.loaded) {
4. $("<img />")
5. .bind("load", function () {
6. $(self)
7. .hide()
8. .attr("src", $(self).attr("original"))
9. [settings.effect](settings.effectspeed);
10. self.loaded = true;
11. })
12. .attr("src", $(self).attr("original"));
13. };
14. });
15. /* When wanted event is triggered load original image */
16. /* by triggering appear.                              */
17. if ("scroll" != settings.event) {
18. $(self).bind(settings.event, function (event) {
19. if (!self.loaded) {
20. $(self).trigger("appear");
21. }
22. });
23. }
24. });
25. /* Force initial check if images should appear. */
26. $(settings.container).trigger(settings.event);
27. return this;
28. };
29. /* Convenience methods in jQuery namespace.           */
30. /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */
31. $.belowthefold = function (element, settings) {
32. if (settings.container === undefined || settings.container === window) {
33. var fold = $(window).height() + $(window).scrollTop();
34. } else {
35. var fold = $(settings.container).offset().top + $(settings.container).height();
36. }
37. return fold <= $(element).offset().top - settings.threshold;
38. };
39. $.rightoffold = function (element, settings) {
40. if (settings.container === undefined || settings.container === window) {
41. var fold = $(window).width() + $(window).scrollLeft();
42. } else {
43. var fold = $(settings.container).offset().left + $(settings.container).width();
44. }
45. return fold <= $(element).offset().left - settings.threshold;
46. };
47. $.abovethetop = function (element, settings) {
48. if (settings.container === undefined || settings.container === window) {
49. var fold = $(window).scrollTop();
50. } else {
51. var fold = $(settings.container).offset().top;
52. }
53. return fold >= $(element).offset().top + settings.threshold + $(element).height();
54. };
55. $.leftofbegin = function (element, settings) {
56. if (settings.container === undefined || settings.container === window) {
57. var fold = $(window).scrollLeft();
58. } else {
59. var fold = $(settings.container).offset().left;
60. }
61. return fold >= $(element).offset().left + settings.threshold + $(element).width();
62. };
63. /* Custom selectors for your convenience.   */
64. /* Use as $("img:below-the-fold").something() */
65. $.extend($.expr[':'], {
66. "below-the-fold": "$.belowthefold(a, {threshold : 0, container: window})",
67. "above-the-fold": "!$.belowthefold(a, {threshold : 0, container: window})",
68. "right-of-fold": "$.rightoffold(a, {threshold : 0, container: window})",
69. "left-of-fold": "!$.rightoffold(a, {threshold : 0, container: window})"
70. });
71. })(jQuery);

            /* When appear is triggered load original image. */
            $(self).one("appear", function () {
                if (!this.loaded) {
                    $("<img />")
.bind("load", function () {
    $(self)
.hide()
.attr("src", $(self).attr("original"))
[settings.effect](settings.effectspeed);
    self.loaded = true;
})
.attr("src", $(self).attr("original"));
                };
            });
            /* 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[':'], {
        "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);

二、scrollLoading实现

<script src="/js/lazyload/jquery.scrollLoading.js" type="text/javascript"></script><script type="text/javascript" src="/js/lazyload//jquery_002.js"></script> < script type="text/javascript" src="/js/lazyload//jquery.js"></script> < script> $(function() {  $(".scrollLoading").scrollLoading();  }); < /script>

HTML：

<img class="scrollLoading" style="background: url(&quot;/js/lazyload/pixel.gif&quot;) no-repeat scroll center center transparent;" src="/js/lazyload/pixel.gif" style="WIDTH: 526px; HEIGHT: 293px" data-url="真实路径"/>

scrollLoading的实现相对而言比较麻烦一下

如果需要对应的JS包请去下载：

http://download.csdn.net/detail/ning109314/3882760