LazyLoad.js及scrollLoading.js延迟加载网页图片
cyjsky 2016-11-15
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($){
$("img").lazyload({
effect : "fadeIn"
});
});
</script>
网上找到一个更好点的处理方式，以下方式转自http://www.poluoluo.com/jzxy/201110/145261.html：
<script type="text/javascript">
//首先用JQ判断浏览器类型及版本，如果是IE8以下的浏览器就用effect=show，否则就用effect=fadeIn，判断浏览器版本函数如下
function checkbrowse() {
var ua = navigator.userAgent.toLowerCase();
var is = (ua.match(/\b(chrome|opera|safari|msie|firefox)\b/) || ['', 'mozilla'])[1];
var r = '(?:' + is + '|version)[\\/: ]([\\d.]+)';
var v = (ua.match(new RegExp(r)) || [])[1];
jQuery.browser.is = is;
jQuery.browser.ver = v;
return {
'is': jQuery.browser.is,
'ver': jQuery.browser.ver
}
}
//改造Jquery.LazyLoad.js函数，根据浏览器版本来显示不同的滤镜效果
var public = checkbrowse();
var showeffect = "";
if ((public['is'] == 'msie' && public['ver'] < 8.0)) {
showeffect = "show"
} else {
showeffect = "fadeIn"
}
jQuery(document).ready(function($) {
$("img").lazyload({
placeholder: "http://demo.jb51.net/js/2011/lazyload/Js/lazyload/grey.gif",
effect: showeffect,
failurelimit: 10
})
});
</script>
html:
<img src="/js/lazyload/pixel.gif" original="真实图片路径" />
而LazyLoad只是给你一个延迟加载的假象，每次图片都会加载两次，完全就是一个假象的延迟加载。可以修改LazyLoad文件实现真实延迟加载，本人比较懒，就直接在网上找了一个修改好的，嘿嘿
- /*
- * Lazy Load - jQuery plugin for lazy loading images
- *
- * Copyright (c) 2007-2009 Mika Tuupola
- *
- * Licensed under the MIT license:
- * http://www.opensource.org/licenses/mit-license.php
- *
- * Project home:
- * http://www.appelsiini.net/projects/lazyload
- *
- * Version: 1.5.0
- *
- */
- (function ($) {
- $.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
- /* 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("/js/lazyload/pixel.gif") 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：
