JavaScript實(shí)現(xiàn)無窮滾動(dòng)加載數(shù)據(jù)

首先實(shí)現(xiàn)滾動(dòng)要借助onscroll事件處理程序。

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無窮滾動(dòng)就是滑動(dòng)滾動(dòng)條，實(shí)現(xiàn)數(shù)據(jù)塊的無窮加載。

我們以瀑布流的布局來實(shí)現(xiàn)無窮加載。瀑布流就是一些等寬不等高的數(shù)據(jù)塊布局。在滾動(dòng)條下拉時(shí)，它會(huì)進(jìn)行加載。那么問題就是在判斷什么時(shí)候應(yīng)該加載。

JavaScript實(shí)現(xiàn)無窮滾動(dòng)加載數(shù)據(jù)

我們首先應(yīng)該明白瀑布流布局的特點(diǎn)。它將下一個(gè)圖片總是放在當(dāng)前列數(shù)最低的那一列。所以當(dāng)加載最后一個(gè)藍(lán)色的圖片時(shí)，也就無疑是最后一個(gè)圖片了。所以要判斷該圖片加載到什么程度來觸發(fā)滾動(dòng)事件。
圖上灰色的表示頁(yè)面的大小，后面藍(lán)色邊框表示窗口的大小。當(dāng)拖動(dòng)滾動(dòng)條時(shí)，灰色部分上移。我們希望頁(yè)面最后一個(gè)圖片（藍(lán)色圖片）加載一半時(shí)觸發(fā)滾動(dòng)事件。那么就要形成參照。

下來寫代碼：

//檢測(cè)是否具備滾動(dòng)條加載數(shù)據(jù)塊的條件
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是根據(jù)類名查找元素集合的自己寫的函數(shù)，待會(huì)兒會(huì)附上源碼

我們要進(jìn)行加載的數(shù)據(jù)塊的格式是這樣的.每個(gè)圖片被一個(gè)class= pic的div包裹。最后整體屬于父元素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>

首先我們要加載的數(shù)據(jù)塊應(yīng)該是從后臺(tái)傳過來的，在這里我們用json模擬一下就可以：

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

比如這個(gè)就是后臺(tái)傳過來的數(shù)據(jù)。

上面的函數(shù)返回一個(gè)布爾值，當(dāng)為true時(shí)，觸發(fā)滾動(dòng)事件。

 window.onscroll = function(){
 var oparent = document.getElementById('main');
 //當(dāng)滿足加載條件時(shí)，就要向頁(yè)面中加載數(shù)據(jù)塊
 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');
  }
 }
}

附上源碼：

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代碼：

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);

 //計(jì)算整個(gè)頁(yè)面顯示的列數(shù)

 var oBoxW = oBoxs[0].offsetWidth;

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

 //設(shè)置main的寬度，并且居中

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

 //找出高度最小的圖片，將下一個(gè)圖片放在下面

 //定義一個(gè)數(shù)組，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();//用來獲取所有class為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;
}


//獲取當(dāng)前最小值得下標(biāo)
function getMinhIndex(array,min){

 for(var i in array){

  if(array[i] == min)

   return i;
 }
}

//檢測(cè)是否具備滾動(dòng)條加載數(shù)據(jù)塊的條件
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?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持創(chuàng)新互聯(lián)。

標(biāo)題名稱：JavaScript實(shí)現(xiàn)無窮滾動(dòng)加載數(shù)據(jù)
標(biāo)題路徑：http://muchs.cn/article0/pdgdio.html

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