JavaScript实现无穷滚动加载数据

发布于 2017-06-15 10:47:08 | 135 次阅读 | 评论: 0 | 来源: 网友投递

JavaScript客户端脚本语言

Javascript 是一种由Netscape的LiveScript发展而来的原型化继承的基于对象的动态类型的区分大小写的客户端脚本语言，主要目的是为了解决服务器端语言，比如Perl，遗留的速度问题，为客户提供更流畅的浏览效果。

这篇文章主要为大家详细介绍了JavaScript实现无穷滚动加载数据，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

首先实现滚动要借助onscroll事件处理程序。

无穷滚动就是滑动滚动条，实现数据块的无穷加载。

我们以瀑布流的布局来实现无穷加载。瀑布流就是一些等宽不等高的数据块布局。在滚动条下拉时，它会进行加载。那么问题就是在判断什么时候应该加载。

我们首先应该明白瀑布流布局的特点。它将下一个图片总是放在当前列数最低的那一列。所以当加载最后一个蓝色的图片时，也就无疑是最后一个图片了。所以要判断该图片加载到什么程度来触发滚动事件。
图上灰色的表示页面的大小，后面蓝色边框表示窗口的大小。当拖动滚动条时，灰色部分上移。我们希望页面最后一个图片（蓝色图片）加载一半时触发滚动事件。那么就要形成参照。

下来写代码：


//检测是否具备滚动条加载数据块的条件
function checkScrollSlide(){
 var oparent = document.getElementById('main');
 var oBoxs = getByClass(oparent,'box');
 var scrollH = document.body.scrollTop || document.documentElement.scrollTop + document.body.clientHeight || document.documentElement.clientHeight;
 var lastBoxH = oBoxs[oBoxs.length - 1].offsetTop + Math.floor(oBoxs[oBoxs.length - 1].offsetHeight/2);

 return (lastBoxH < scrollH )? true : false;
}

getClass是根据类名查找元素集合的自己写的函数，待会儿会附上源码

我们要进行加载的数据块的格式是这样的.每个图片被一个class= pic的div包裹。最后整体属于父元素main


<div id = "main">
 <div class = "box">
  <div class = "pic">
   <img src = "images/0.jpg">
  </div>
 </div>
 <div class = "box">
  <div class = "pic">
   <img src = "images/1.jpg">
  </div>
 </div>
 <div class = "box">
  <div class = "pic">
   <img src = "images/2.jpg">
  </div>
 </div>
<div>

首先我们要加载的数据块应该是从后台传过来的，在这里我们用json模拟一下就可以：

var DataIn = {"data":[{"src":'0.jpg'},{"src":'1.jpg'},{"src":'2.jpg'},{"src":'3.jpg'},{"src":'4.jpg'},{"src":'5.jpg'}]};

比如这个就是后台传过来的数据。

上面的函数返回一个布尔值，当为true时，触发滚动事件。


 window.onscroll = function(){
 var oparent = document.getElementById('main');
 //当满足加载条件时，就要向页面中加载数据块
 if(checkScrollSlide){
  for(var i = 0; i< DataIn.data.length; i++){
    var oBox = document.createElement('div');
    oBox.className = 'box';
    oparent.appendChild(oBox);

    var opic = document.createElement('div');
    opic.className = 'pic';
    oBox.appendChild(opic);

    var oImg = document.createElement('img');
    oImg.src = './images/'+DataIn.data[i].src;
    opic.appendChild(oImg);

   }
   waterFull('main','box');
  }
 }
}

附上源码：

css和html


<!DOCTYPE html>
<html>
<head>
<meta charset = "utf-8" />
<script src = "./jswaterfll.js"></script>
 <title>瀑布流布局</title>
 <style type="text/css">
 *{
 padding: 0px;
 margin: 0px;
 }

 #main{
 position: relative;

 }
 .box{
/* display: inline-block;*/
 padding: 15px 0px 0px 15px;
 float: left;

 }
 .pic{
 padding: 10px;
 border-radius: 5px;
 border:1px solid #ccc;
 box-shadow: 0 0 5px #ccc;
 }

 .pic img{
 width: 165px;
 height: auto;
 }
 </style>
</head>
<body>
<div id = 'main'>
 <div class = "box">
 <div class = "pic">
  <img src = "images/3.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/4.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/20.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/21.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/2.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/3.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/4.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/5.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/6.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/7.jpg">
 </div>
 </div>

 <div class = "box">
 <div class = "pic">
  <img src = "images/8.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/9.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/10.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/11.jpg">
 </div>
 </div>

 <div class = "box">
 <div class = "pic">
  <img src = "images/17.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/18.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/19.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/4.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/5.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/6.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/7.jpg">
 </div>
 </div>

 <div class = "box">
 <div class = "pic">
  <img src = "images/8.jpg">
 </div>
 </div>

 <div class = "box">
 <div class = "pic">
  <img src = "images/11.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/12.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/13.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/14.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/15.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/16.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/17.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/18.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/19.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/20.jpg">
 </div>
 </div>
 <div class = "box">
 <div class = "pic">
  <img src = "images/21.jpg">
 </div>
 </div>
</div>
</body>
</html>

js代码：


window.onload = function(){
 waterFull('main','box');

 var DataIn = {"data":[{"src":'0.jpg'},{"src":'1.jpg'},{"src":'2.jpg'},{"src":'3.jpg'},{"src":'4.jpg'},{"src":'5.jpg'}]};
 window.onscroll = function(){
  var oparent = document.getElementById('main');
  if(checkScrollSlide){
   for(var i = 0; i< DataIn.data.length; i++){
    var oBox = document.createElement('div');
    oBox.className = 'box';
    oparent.appendChild(oBox);

    var opic = document.createElement('div');
    opic.className = 'pic';
    oBox.appendChild(opic);

    var oImg = document.createElement('img');
    oImg.src = './images/'+DataIn.data[i].src;
    opic.appendChild(oImg);

   }
   waterFull('main','box');
  }
 }
}

function waterFull(parent,children){
 var oParent = document.getElementById(parent);
 //var oBoxs = parent.querySelectorAll(".box");

  var oBoxs = getByClass(oParent,children);

 //计算整个页面显示的列数

 var oBoxW = oBoxs[0].offsetWidth;

 var cols = Math.floor(document.documentElement.clientWidth/oBoxW);

 //设置main的宽度，并且居中

 oParent.style.cssText = 'width:'+oBoxW * cols +'px; margin: 0 auto';

 //找出高度最小的图片，将下一个图片放在下面

 //定义一个数组，存放每一列的高度，初始化存的是第一行的所有列的高度

 var arrH = [];

 for(var i = 0; i< oBoxs.length ; i++){
  if(i < cols){
   arrH.push(oBoxs[i].offsetHeight);
  }
  else{
   var minH = Math.min.apply(null,arrH);

   var minIndex = getMinhIndex(arrH,minH);

   oBoxs[i].style.position = 'absolute';
   oBoxs[i].style.top= minH + 'px';
   //oBoxs[i].style.left = minIndex * oBoxW + 'px'; 
   oBoxs[i].style.left = oBoxs[minIndex].offsetLeft+'px';

   arrH[minIndex] += oBoxs[i].offsetHeight; 
  }
 }


}
function getByClass(parent,className){

 var boxArr = new Array();//用来获取所有class为box的元素

 oElement = parent.getElementsByTagName('*');

 for (var i = 0; i <oElement.length; i++) {

  if(oElement[i].className == className){

   boxArr.push(oElement[i]);

  }
 };
 return boxArr;
}


//获取当前最小值得下标
function getMinhIndex(array,min){

 for(var i in array){

  if(array[i] == min)

   return i;
 }
}

//检测是否具备滚动条加载数据块的条件
function checkScrollSlide(){
 var oparent = document.getElementById('main');
 var oBoxs = getByClass(oparent,'box');
 var scrollH = document.body.scrollTop || document.documentElement.scrollTop + document.body.clientHeight || document.documentElement.clientHeight;
 var lastBoxH = oBoxs[oBoxs.length - 1].offsetTop + Math.floor(oBoxs[oBoxs.length - 1].offsetHeight/2);

 return (lastBoxH < scrollH )? true : false;
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持phperz。

JavaScript实现无穷滚动加载数据

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