Native ajax implements pull-up loading function

This time I will bring you the pull-up loading function of native ajax. What are the precautions for native ajax to realize the pull-up loading function. The following is a practical case, let's take a look.

The idea of ​​pull-up loading

1 Pull-up loading is to trigger the ajax event to request data when the screen is pulled to the bottom

2. All the codes below that need to obtain the height of the screen, document height and scrolling height are already compatible and can be used directly.

Javascript:
alert(document.body.clientWidth);  //网页可见区域宽(body)
alert(document.body.clientHeight);  //网页可见区域高(body)
alert(document.body.offsetWidth);  //网页可见区域宽(body)，包括border、margin等
alert(document.body.offsetHeight);  //网页可见区域宽(body)，包括border、margin等
alert(document.body.scrollWidth);  //网页正文全文宽，包括有滚动条时的未见区域
alert(document.body.scrollHeight);  //网页正文全文高，包括有滚动条时的未见区域
alert(document.body.scrollTop);   //网页被卷去的Top(滚动条)
alert(document.body.scrollLeft);   //网页被卷去的Left(滚动条)
alert(window.screenTop);      //浏览器距离Top
alert(window.screenLeft);      //浏览器距离Left
alert(window.screen.height);    //屏幕分辨率的高
alert(window.screen.width);     //屏幕分辨率的宽
alert(window.screen.availHeight);   //屏幕可用工作区的高
alert(window.screen.availWidth);   //屏幕可用工作区的宽
 
 
 
Jquery
alert($(window).height());       //浏览器当前窗口可视区域高度
alert($(document).height());      //浏览器当前窗口文档的高度
alert($(document.body).height());    //浏览器当前窗口文档body的高度
alert($(document.body).outerHeight(true)); //浏览器当前窗口文档body的总高度 包括border padding margin
alert($(window).width());       //浏览器当前窗口可视区域宽度
alert($(document).width());      //浏览器当前窗口文档对象宽度
alert($(document.body).width());    //浏览器当前窗口文档body的宽度
alert($(document.body).outerWidth(true)); //浏览器当前窗口文档body的总宽度 包括border padding margin

//获取滚动条当前的位置
 function getScrollTop() {
  var scrollTop = 0;
  if (document.documentElement && document.documentElement.scrollTop) {
   scrollTop = document.documentElement.scrollTop;
  } else if (document.body) {
   scrollTop = document.body.scrollTop;
  }
  return scrollTop;
 }
 //获取当前可视范围的高度
 function getClientHeight() {
  var clientHeight = 0;
  if (document.body.clientHeight && document.documentElement.clientHeight) {
   clientHeight = Math.min(document.body.clientHeight, document.documentElement.clientHeight);
  } else {
   clientHeight = Math.max(document.body.clientHeight, document.documentElement.clientHeight);
  }
  return clientHeight;
 }
 //获取文档完整的高度
 function getScrollHeight() {
  return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
 }

var upDown = function (opt) {
  opt = opt || {};
  var up = opt.up || function () {
  };
  window.onscroll = function () {
if (getScrollTop() + getClientHeight() == getScrollHeight()) { //距离顶部+当前高度 >=文档总高度 即代表滑动到底部
    if(is_scroll === true){ //当这个为true的时候调用up方法 ....is_scroll没看懂往下看
 up();
 }}
  }
 };

3. First, the first page must be loaded by default. , call the upDown method in window.onload

window.onload = function () {
  getData();//页面加载完就显示了第一页
  upDown({
   up: getData
  });
 }

4. When the page scrolls to the bottom, the up() method is triggered, and up calls the getdata method. Here is how to get the data

Define two variables globally var is_scroll = true; var count = 0;

var is_scroll = true;
var count = 0;
function getAjax() {
  var el, li; 
  var xhr = new XMLHttpRequest();
  xhr.open('get', 'page' + count + '.json'); 
  xhr.send();
  xhr.onreadystatechange = function () {
   var loadingEnd = document.getElementById('loadingEnd');
   var dropLoad = document.getElementById('dropLoad');
   if (xhr.readyState === 4 && xhr.status === 200) {
　　　　　　　　 
    var res = xhr.responseText;
    var data = JSON.parse(res);
    allData = allData.concat(data);//新的一页拼接到后面;
    if (data.length === 0) { //当获取到的数据长度为0 说明没有count+是请求不到数据了
      is_scroll = true // 定义为true 
     loadingEnd.style.display = 'block'; //显示没有数据
    }
    el = document.querySelector("#wrapper ul"); 
    for (var k in data) { //遍历获取到的每一条数据
     li = document.createElement('li'); // 创建节点
     li.innerHTML = "<p class=&#39;item-top&#39;><span class=&#39;item-title&#39;>" + data[k].name + "</span><span class=&#39;item-money&#39;>" + data[k].money + "</span></p><p class=&#39;item-time&#39;>" + data[k].time + "</p><p class=&#39;bottom-line&#39;></p>";
     el.appendChild(li, el.childNodes[0]);
    }
    dropLoad.style.display = 'block';//显示加载中
   } else { //这个可有可无 是个假的 不管请求没有请求到都会有个加载中的动画
    setTimeout(function () {
     dropLoad.style.display = 'none';
    }, 500)
   }
  };
 }

<style>
  .drop-load {
   text-align: center;
   height: 80px;
   line-height: 50px;
  }
  .drop-load .loading {
   display: inline-block;
   height: 15px;
   width: 15px;
   border-radius: 100%;
   margin: 6px;
   border: 2px solid #666;
   border-bottom-color: transparent;
   vertical-align: middle;
   -webkit-animation: rotate 0.75s linear infinite;
   animation: rotate 0.75s linear infinite;
  }
  @-webkit-keyframes rotate {
   0% {
    -webkit-transform: rotate(0deg);
   }
   50% {
    -webkit-transform: rotate(180deg);
   }
   100% {
    -webkit-transform: rotate(360deg);
   }
  }
  @keyframes rotate {
   0% {
    transform: rotate(0deg);
   }
   50% {
    transform: rotate(180deg);
   }
   100% {
    transform: rotate(360deg);
   }
  }
  .loadingEnd {
   font-size: 0.3rem;
   color: black;
   width: 100%;
   height: 40px;
   text-align: center;
  }
 </style>

<body>
<p>
 <ul>
 </ul>
</p>
<p id="dropLoad" class="drop-load" style="display: none">
 <span class="loading"></span>
 <span>加载中</span>
</p>
<p id="loadingEnd" class="loadingEnd" style="display: none">到底了</p>
</body>

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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