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Implementation and usage of unordered preloading of images in jquery

不言Original: 2018-08-13 10:40:151531browse

The content of this article is about the implementation and usage of unordered image preloading in jquery. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

/图片无序预加载
(function($){


function Preload(imgs,fns){

this.imgs=(typeof imgs==="string")?[imgs]:imgs;

this.fns=$.extend({},Preload.fns,fns);//把fns 覆盖到Preload上 然后添加到{}返回

if(this.fns.loadMethod=="unorderload"){//是无序 还是有序

this._unorderload();
}
else{

this._orderload();

}
}

Preload.fns={
loadMethod:null,//有序还是无序的方式
eachLoadImg:null, //每张图片加载完所执行的函数
allLoadImg:null //所有图片加载完所要执行的函数
}
Preload.prototype._orderload=function(){
var imgs=this.imgs,
len=imgs.length,
fns=this.fns,
num=0;
function load(){
var imgObj=new Image();
$(imgObj).on("load error",function(){
fns.each && fns.each(); //存在 才会执行
if(num<len){
load(); //没有加载完就继续加载 函数执行是有顺序的
}
else{
fns.allLoadImg && fns.allLoadImg();//加载完全部
}
});
imgObj.src=imgs[num];
num++;
}
load();
}
Preload.prototype._unorderload=function(){
var imgs=this.imgs,
len=imgs.length,
fns=this.fns,
num=0;
$.each(imgs,function(i,src){

if(typeof src!="string") return;

var imgObj=new Image();
$(imgObj).on("load error",function(){

fns.eachLoadImg && fns.eachLoadImg(num,len);

if( num==len-1){

fns.allLoadImg && fns.allLoadImg();
}
num++;
});
imgObj.src=src;

});

}
$.extend({             //给jQuery上增加新函数

preload:function(imgs,fns){

new Preload(imgs,fns);

}

});

})(jQuery);

How to use

<!doctype html>
<html>
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>有序预加载</title>
  <style>
        *{margin: 0; padding: 0;}
       
           img{
            width:100%;
            vertical-align:top;
           
           }
       .imgBox{
         width:500px;
         margin:100px auto;
         
       
       }
        #prevImg, #nextImg{
          
          width:60px;
          font-size:15px;
          height:30px;
          line-height:30px;
          text-align:center;
          background: #686868;
          position:absolute;
          color:#000;
          text-decoration:none;
          margin-top:-50px;
        }

        #prevImg{
            
          left:40%;
          
        }

        #nextImg{
         
         left:55%;
        
        }

  </style>
  <script src="js/jquery-3.2.1.js"></script>
  <script src="js/unorderload.js"></script>
  <script>
     
     $(function(){
     
     
     
     var imgs=["img/0.jpg","img/1.jpg","img/2.jpg","img/3.jpg","img/4.jpg","img/5.jpg","img/6.jpg","img/7.jpg"];
     var len=imgs.length;
     var index=0;
      $.preload(imgs,{});

     $("#control-img-btn").on("click","a",function(){
         

        
          if($(this).hasClass("prevImg")){
               
                index=Math.max(0,--index);  //上一张
          }

          else{
               
               index=Math.min(len-1,++index);//下一张
          
          }

          $("#imgBox img").attr("src",imgs[index]);
     
     
     });

     });
       


  </script>
 </head>
 <body>
     <div id="imgBox">
       <img />
     </div>
     <p id="control-img-btn">
       <a href="javascript:;" id="prevImg">上一页</a>
       <a href="javascript:;" id="nextImg">下一页</a>
     </p>
 </body>
</html>

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