原生js判斷某個區域的滾動條滾動到了底部

原生js判斷某個區域的滾動條滾動到了底部###

講解==》

關系公式：element.scrollHeight - element.scrollTop === element.clientHeight
解釋：此公式可以用於判斷是否滾動到底
你必須知道這個方法 可以判斷滾動條滾動到了底部哈！

element.scrollHeight 是獲取這個元素區域的實際高度（包含被隱藏起來的高度）
element.scrollTop是獲取滾動條距離頂部的實際距離（包含被隱藏起來的高度）
element.clientHeight: 就是元素內部（可見高度） + 自身padding

在生命周期函數中 給滾動區域的元素注冊滾動事件
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/element-ui@2.4.11/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","最后一條數據了",
			  ],
			  boxScrollpositionHeight:0,
			  boxElement:"",
			  boxscrollPosition:0,//滾動條所在的高度()
		    }
		},
		mounted () {
			 this.boxElement=document.getElementById("box"); 
			
		   	this.boxElement.addEventListener('scroll', this.doSomething);
			
			// 獲取滾動條滾動區域盒子的高度
			
			this.boxScrollpositionHeight=this.boxElement.offsetHeight;
			console.log("div內容區域的實際高度",this.boxElement.scrollHeight)
		},
		methods: {
		    doSomething(){
			 
			    //此時滾動條所在的高度 
			    let scrollcurHeight=this.boxElement.scrollTop;
				
				
				console.log("滾動條距離頂部的實際高度",this.boxElement.scrollTop)
				console.log("hah",this.boxElement.clientHeight)
				
				
				// 關系公式：element.scrollHeight - element.scrollTop === element.clientHeight
                // 解釋：此公式可以用於判斷是否滾動到底
　　
					
				if(this.boxElement.scrollHeight-this.boxElement.scrollTop===this.boxElement.clientHeight){
					console.log("滾動到底部了",)
				} 
		    }
		 },
		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>