原生js判断某个区域的滚动条滚动到了底部

原生js判断某个区域的滚动条滚动到了底部

讲解==》

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
你必须知道这个方法 可以判断滚动条滚动到了底部哈！

element.scrollHeight 是获取这个元素区域的实际高度（包含被隐藏起来的高度）
element.scrollTop是获取滚动条距离顶部的实际距离（包含被隐藏起来的高度）
element.clientHeight: 就是元素内部（可见高度） + 自身padding

在生命周期函数中 给滚动区域的元素注册滚动事件
element.addEventListener(‘scroll‘, this.doSomething);

<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//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>