How to implement simple vue infinite loading instructions-JS Tutorial-php.cn

This article mainly introduces the method of implementing simple vue infinite loading instructions. It has certain reference value. Now I share it with you. Friends in need can refer to the custom instructions in

vue. It operates on the underlying DOM. Let's introduce how to customize a simple instruction by scrolling to the bottom to load data and achieving infinite loading.

The principle of infinite loading is to monitor the scrolling event. Each time you scroll, you must obtain the scrolled distance. If the scrolling distance plus the browser window height is greater than or equal to the content height, the function will be triggered. Download Data.

First introduce how to achieve infinite loading without using vue.

Do not use frames

The first is html:

<!DOCTYPE html><html lang="en">
<head><meta charset="UTF-8">
<title>实现滚动加载</title>
<style>
 * {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  }
 li, ul {
  list-style: none;
 }
 .container {
  width: 980px;
  margin: 0 auto;
 }
 .news__item {
  height: 80px;
  margin-bottom: 20px;
  border: 1px solid #eee;
 }</style>
</head>
<body>
<p class="container">
 <ul class="news" id="news">
  <li class="news__item">1、hello world</li>
  <li class="news__item">2、hello world</li>
  <li class="news__item">3、hello world</li>
  <li class="news__item">4、hello world</li>
  <li class="news__item">5、hello world</li>
  <li class="news__item">6、hello world</li>
  <li class="news__item">7、hello world</li>
  <li class="news__item">8、hello world</li>
  <li class="news__item">9、hello world</li>
  <li class="news__item">10、hello world</li>
 </ul>
</p>
</body>
</html>

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Open the browser and adjust the browser window Height to make the page scrollable.

First understand the three variables

document.body.scrollTop The distance the scroll bar scrolls
window. innerHeight browser window height
document.body.clientHeight content height

corresponds to the above principle is

window.addEventListener(&#39;scroll&#39;, function() {
 var scrollTop = document.body.scrollTop;
 if(scrollTop + window.innerHeight >= document.body.clientHeight) {
  // 触发加载数据    
  loadMore();
 }
});
function loadMore() {
 console.log(&#39;加载数据&#39;)&#39;
}

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loadMore() function is to get the data from the interface, assemble the html, and insert it behind the original node.

// 表示列表的序号
var index = 10;
function loadMore() {
 var content = &#39;&#39;;
 for(var i=0; i< 10; i++) {
  content += &#39;<li class="news__item">&#39;+(++index)+&#39;、hello world</li>&#39;  
 }
 var node = document.getElementById(&#39;news&#39;);
 // 向节点内插入新生成的数据  
 var oldContent =   node.innerHTML;
 node.innerHTML = oldContent+content;
}

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This achieves infinite loading.

Use instructions to implement in vue

Why do we need to use instructions to implement it? It seems that only instructions can get the underlying DOM? To achieve infinite loading, you need to obtain the content height.

First initialize a project and add a component to display the list.

// components/Index.vue
<template>
 <p>
  <ul class="news">
   <li class="news__item" v-for="(news, index) in newslist">
    {{index}}-{{news.title}}
   </li>
  </ul>
 </p>
</template>
<style>
 .news__item {
  height: 80px;
  border: 1px solid #ccc;
  margin-bottom: 20px;
 }
</style>
<script>
 export default{
  data(){
   return{
    newslist: [
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;},
     {title: &#39;hello world&#39;}
    ]
   }
  }
 }
</script>

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OK, now start writing instructions. From the traditional implementation, we learned that we need to register to listen for scroll events and get the content height at the same time.

directives: {
 scroll: {
  bind: function (el, binding){
   window.addEventListener(&#39;scroll&#39;, ()=> {
    if(document.body.scrollTop + window.innerHeight >= el.clientHeight) {
     console.log(&#39;load data&#39;);
    }
   })
  }
 }
}

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First, the scroll instruction is registered in the component, and then when the instruction is bound to the component for the first time, that is, corresponding to the bind hook, the scroll is registered monitor.

Hook functions are functions that are called when some life cycles change. bind is called when it is bound to the component for the first time, and unbind is called when the instruction is unbound from the component.

You can also notice that bind corresponds to two parameters of the function, el and binding. These are hook function parameters. For example, el corresponds to the bound node. Binding has a lot of data, such as the ones passed to the instructions. Parameters etc.

The el.clientHeight below represents the content height of the node that obtains the binding instruction.

As before, determine whether the scroll height plus the window height is greater than the content height.

Bind the command to the node:

<template>
 <p v-scroll="loadMore">
  <ul class="news">
   <li class="news__item" v-for="(news, index) in newslist">
    {{index}}-{{news.title}}
   </li>
  </ul>
 </p>
</template>

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You can see that a value is passed to the command, which is the function to load data:

methods: {
 loadMore() {
  let newAry = [];
  for(let i = 0; i < 10; i++) {
   newAry.push({title: &#39;hello world&#39;})
  }
  this.newslist = [...this.newslist, ...newAry];
 }
}

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Of course, now when scrolling to the bottom, only load data will be printed. Just change this to call a function and it will be OK:

 window.addEventListener(&#39;scroll&#39;, ()=> { 
 if(document.body.scrollTop + window.innerHeight >= el.clientHeight) {  
  let fnc = binding.value;  
  fnc(); 
 }
})

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The loadMore of v-scroll="loadMore" can be obtained from the binding of the hook function parameter.

At this point, a simple command is completed.

Optimization

The above example does not actually obtain data from the interface, so there is a hidden bug: when the interface response is very slow, scroll to the end When the data is being loaded, a slight scrolling will still trigger the data acquisition function, which will cause multiple interface requests at the same time and return a large amount of data at once.

The solution is to add a global variable scrollDisable. When the loading data function is triggered for the first time, set the value to true, and use this value to determine whether to execute the loading function.

Take ordinary implementation as an example:

var scrollDisable = false;
window.addEventListener(&#39;scroll&#39;, function() {
 var scrollTop = document.body.scrollTop;
 if(scrollTop + window.innerHeight >= document.body.clientHeight) {
  // 触发加载数据    
  if(!scrollDisable) {
   // 
   loadMore(); 
  } 
 }
});
// 表示列表的序号
var index = 10;
function loadMore() {
  // 开始加载数据，就不能再次触发这个函数了
 scrollDisable = true;
 var content = &#39;&#39;;
 for(var i=0; i< 10; i++) {
  content += &#39;<li class="news__item">&#39;+(++index)+&#39;、hello world</li>&#39;  
 }
 var node = document.getElementById(&#39;news&#39;);
 // 向节点内插入新生成的数据  
 var oldContent =   node.innerHTML;
 node.innerHTML = oldContent+content;
 // 插入数据完成后  
 scrollDisable = false;
}

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