<template>    <div class="comment">    	<div class="comment-wrap" ref="wrapper">	    <ul class="list" ref="list">    	        <li v-for="item in list" :key="item.id">    		    <span class="name">{{item.name}}：</span>    		    <span class="content">{{item.content}}</span>    	        </li>            </ul>    	</div>    	<div class="rest-nums" v-show="restComment" @click="scrollBottom">{{restComment}}條新消息</div>    </div></template>

<script>import smoothscroll from 'smoothscroll-polyfill';import { debounce, isScrollBottom } from '../utils/utils';smoothscroll.polyfill(); // 移動端scrollTo behavior: "smooth"動畫失效的polyfillexport default {  data() {    return {        list: [],        restComment: 0,        restNums: 0,        wrapperDom: null,        listDom: null,        wrapperHeight: 0    };  },  mounted() {     this.initDom();     // ajax...     const data = new Array(20).fill('');     this.queue(data);     setTimeout(() => {         const list = new Array(10).fill('');	 this.queue(list);      }, 30000);  },  methods: {      initDom() {          this.wrapperDom = this.$refs.wrapper;          this.listDom = this.$refs.list;          this.wrapperHeight = this.wrapperDom.offsetHeight;      },      addTimeOut(opt) {    	   return new Promise((resolve, reject) => {    		setTimeout(() => {    			this.addComment(opt);    			resolve()    		}, 500);    	   });       },	// 隊列添加消息	async queue(data) {    	    for (let i = 0; i < data.length; i++) {    		const opt = {    			name: i + "-用戶名",    			content: i + "-評論內容",    			id: Date.now()    		}    		await this.addTimeOut(opt);    	    }	},        addScroll() {            debounce(this.listScroll, 200);            this.isBindScrolled = true;        },        listScroll() {            const ele = this.wrapperDom;            const isBottom = isScrollBottom(ele, ele.clientHeight);            if (isBottom) {		this.restNums = 0;		this.restComment = 0;            }        },	// 添加評論 如果超過150條就將前50條刪除        addComment(data) {            if (this.list.length >= 150) {                this.list.splice(0, 50);            }	    this.list.push(data);	    this.$nextTick(() => {		this.renderComment();	    });	},	// 渲染評論        renderComment() {            const listHight = this.listDom.offsetHeight;            const diff = listHight - this.wrapperHeight; // 列表高度與容器高度差值	    const top = this.wrapperDom.scrollTop; // 列表滾動高度            if (diff - top < 50) {                 if (diff > 0) {                    if (this.isBindScrolled) {                        this.isBindScrolled = false;                        this.wrapperDom.removeEventListener("scroll", this.addScroll);                    }                    this.wrapperDom.scrollTo({                        top: diff + 10,                        left: 0,                        behavior: "smooth"        	    });                    this.restNums = 0;                }            } else {                ++this.restNums;                if (!this.isBindScrolled) {                    this.isBindScrolled = true;                    this.wrapperDom.addEventListener("scroll", this.addScroll);                }            }	    this.restComment = this.restNums >= 99 ? "99+" : this.restNums;    	},	// 滾動到底部        scrollBottom() {	    this.restNums = 0; // 清除剩余消息	    this.restComment = this.restNums;            this.wrapperDom.scrollTo({                top: this.listDom.offsetHeight,                left: 0,                behavior: "smooth"            });        }    }};</script>

<style scoped>    *{    	padding: 0;    	margin: 0;    }    .comment{    	width: 70%;    	height: 350px;    	position: relative;    	margin: 100px 0 0 20px;    }    .comment-wrap{    	height: 350px;    	overflow-y: scroll;    	-webkit-overflow-scrolling:touch;    }    .comment-wrap li{    	text-align: left;    	line-height: 30px;    	padding-left: 10px;    	background: rgba(0, 0, 0, 0.3);    	margin-top: 5px;    	border-radius: 15px;    	color: #fff;    }    .rest-nums{    	position: absolute;    	height: 24px;    	line-height: 24px;    	color: #f00;    	border-radius: 15px;    	padding: 0 15px;    	bottom: 10px;    	background: #fff;    	font-size: 14px;    	left: 10px;    }</style>

/** * @desc 函數防抖 * @param {需要防抖的函數} func * @param {延遲時間} wait */export function debounce(func, wait = 500) {    // 緩存一個定時器id    let timer = 0;    // 這里返回的函數是每次用戶實際調用的防抖函數    // 如果已經設定過定時器了就清空上一次的定時器    // 開始一個新的定時器，延遲執行用戶傳入的方法    return function (...args) {    	if (timer) clearTimeout(timer)    	timer = setTimeout(() => {    		func.apply(this, args)    	}, wait)    }}/** * @desc 是否滾到到容器底部 * @param {滾動容器} ele  * @param {容器高度} wrapHeight  */export function isScrollBottom(ele, wrapHeight, threshold = 30) {    const h1 = ele.scrollHeight - ele.scrollTop;    const h2 = wrapHeight + threshold;    const isBottom = h1 <= h2;    return isBottom;}