一番下の領域にスクロールするネイティブJSスクロールバーを分析します

一番下の領域にスクロールするネイティブJSスクロールバーを分​​析します

"==説明

関係式：element.scrollHeight - element.scrollTop === element.clientHeightの
説明：この式は決定するために使用することができるかどうかを最終的にスクロール
しますが、この方法は、ハの一番下までスクロールするには、スクロールバーを決定することができることを知っている必要があります！

element.scrollHeightは、素子領域（隠された高さを含む）の実際の高さを取得することである
element.scrollTopは（隠された高さを含む）実際の距離の上部からスクロールバーを取得することである
element.clientHeight：ある内部要素（可視高さ） +自体パディング

領域内の関数への転動体のライフサイクルのスクロールイベント登録
element.addEventListener（「スクロール」、this.doSomething）を 、

  <div id="app">
         <div class="box" id="box"> 
            <div class="demo" v-for="(item,index) in condata" :key="index">{{item}}</div>
         </div>
   </div>

  <!-- import Vue before Element -->
  <script src="https://unpkg.com/vue/dist/vue.js"></script>
  <!-- import JavaScript -->
  <script src="https://unpkg.com/axios/dist/axios.min.js"></script>
  <script src="https://unpkg.com/[email protected]/lib/index.js"></script>
  <script>
    new Vue({
      el: '#app',
        data() {
            return {
                condata:["121212","121212","121212","121212","121212","121212","121212","121212",
               "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212",
               "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","121212",
              "121212","121212","121212","121212","121212","121212","121212","121212","最后一条数据了",
              ],
              boxScrollpositionHeight:0,
              boxElement:"",
              boxscrollPosition:0,//滚动条所在的高度()
            }
        },
        mounted () {
             this.boxElement=document.getElementById("box"); 
            
            this.boxElement.addEventListener('scroll', this.doSomething);
            
            // 获取滚动条滚动区域盒子的高度
            
            this.boxScrollpositionHeight=this.boxElement.offsetHeight;
            console.log("div内容区域的实际高度",this.boxElement.scrollHeight)
        },
        methods: {
            doSomething(){
             
                //此时滚动条所在的高度 
                let scrollcurHeight=this.boxElement.scrollTop;
                
                
                console.log("滚动条距离顶部的实际高度",this.boxElement.scrollTop)
                console.log("hah",this.boxElement.clientHeight)
                
                
                // 关系公式：element.scrollHeight - element.scrollTop === element.clientHeight
                // 解释：此公式可以用于判断是否滚动到底
　　
                    
                if(this.boxElement.scrollHeight-this.boxElement.scrollTop===this.boxElement.clientHeight){
                    console.log("滚动到底部了",)
                } 
            }
         },
        beforeDestroy() {
            let boxscrollPosition=document.getElementById("box");
            boxscrollPosition.removeEventListener('scroll', this.doSomething);
        },
    })
  </script>

  <style type="text/css">
      *{
          padding: 0;
          margin: 0;
      }
      body,html,#app{
          height: 100%;
      }
    .box{
         width: 300px;
         height: calc(100% - 279px);
         background: #0366D6;
         overflow: hidden;
         overflow-y: auto;
        }
        
        .demo{
            height: 30px;
            line-height: 30px;
            border-top:1px solid #ccc;
        }
        
  </style>