一个图片延时加载的实例

js代码:

<script type="javascript">
(function(a,b,c,d){var e=a(b);a.fn.lazyload=function(c){function i(){var b=0;f.each(function(){var c=a(this);if(h.skip_invisible&&!c.is(":visible"))return;if(!a.abovethetop(this,h)&&!a.leftofbegin(this,h))if(!a.belowthefold(this,h)&&!a.rightoffold(this,h))c.trigger("appear"),b=0;else if(++b>h.failure_limit)return!1})}var f=this,g,h={threshold:0,failure_limit:0,event:"scroll",effect:"show",container:b,data_attribute:"src",skip_invisible:!0,appear:null,load:null};return c&&(d!==c.failurelimit&&(c.failure_limit=c.failurelimit,delete c.failurelimit),d!==c.effectspeed&&(c.effect_speed=c.effectspeed,delete c.effectspeed),a.extend(h,c)),g=h.container===d||h.container===b?e:a(h.container),0===h.event.indexOf("scroll")&&g.bind(h.event,function(a){return i()}),this.each(function(){var b=this,c=a(b);b.loaded=!1,c.one("appear",function(){if(!this.loaded){if(h.appear){var d=f.length;h.appear.call(b,d,h)}a("<img />").bind("load",function(){c.hide().attr("src",c.data(h.data_attribute))[h.effect](h.effect_speed),b.loaded=!0;var d=a.grep(f,function(a){return!a.loaded});f=a(d);if(h.load){var e=f.length;h.load.call(b,e,h)}}).attr("src",c.data(h.data_attribute))}}),0!==h.event.indexOf("scroll")&&c.bind(h.event,function(a){b.loaded||c.trigger("appear")})}),e.bind("resize",function(a){i()}),/iphone|ipod|ipad.*os 5/gi.test(navigator.appVersion)&&e.bind("pageshow",function(b){b.originalEvent.persisted&&f.each(function(){a(this).trigger("appear")})}),a(b).load(function(){i()}),this},a.belowthefold=function(c,f){var g;return f.container===d||f.container===b?g=e.height()+e.scrollTop():g=a(f.container).offset().top+a(f.container).height(),g<=a(c).offset().top-f.threshold},a.rightoffold=function(c,f){var g;return f.container===d||f.container===b?g=e.width()+e.scrollLeft():g=a(f.container).offset().left+a(f.container).width(),g<=a(c).offset().left-f.threshold},a.abovethetop=function(c,f){var g;return f.container===d||f.container===b?g=e.scrollTop():g=a(f.container).offset().top,g>=a(c).offset().top+f.threshold+a(c).height()},a.leftofbegin=function(c,f){var g;return f.container===d||f.container===b?g=e.scrollLeft():g=a(f.container).offset().left,g>=a(c).offset().left+f.threshold+a(c).width()},a.inviewport=function(b,c){return!a.rightoffold(b,c)&&!a.leftofbegin(b,c)&&!a.belowthefold(b,c)&&!a.abovethetop(b,c)},a.extend(a.expr[":"],{"below-the-fold":function(b){return a.belowthefold(b,{threshold:0})},"above-the-top":function(b){return!a.belowthefold(b,{threshold:0})},"right-of-screen":function(b){return a.rightoffold(b,{threshold:0})},"left-of-screen":function(b){return!a.rightoffold(b,{threshold:0})},"in-viewport":function(b){return a.inviewport(b,{threshold:0})},"above-the-fold":function(b){return!a.belowthefold(b,{threshold:0})},"right-of-fold":function(b){return a.rightoffold(b,{threshold:0})},"left-of-fold":function(b){return!a.rightoffold(b,{threshold:0})}})})(jQuery,window,document)$(function() {$("img").lazyload({effect:"fadeIn"});});

然后需要在CSS里面IMG标签定义:

background:url("你的图片地址")no-repeat 50% 50%;

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