直播间评论滚动效果,下划查看历史消息并停止滚动,如有新消息会出现新消息提醒,点击滚动到底部。
2.具体代码
<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}}条新消息</div> </div> </template>
<script> import smoothscroll from 'smoothscroll-polyfill'; import { debounce, isScrollBottom } from '../utils/utils'; smoothscroll.polyfill(); // 移动端scrollTo behavior: "smooth"动画失效的polyfill export 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); }); }, // 队列添加消息 async queue(data) { for (let i = 0; i < data.length; i ) { const opt = { name: i "-用户名", content: i "-评论内容", 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; } }, // 添加评论 如果超过150条就将前50条删除 addComment(data) { if (this.list.length >= 150) { this.list.splice(0, 50); } this.list.push(data); this.$nextTick(() => { this.renderComment(); }); }, // 渲染评论 renderComment() { const listHight = this.listDom.offsetHeight; const diff = listHight - this.wrapperHeight; // 列表高度与容器高度差值 const top = this.wrapperDom.scrollTop; // 列表滚动高度 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; }, // 滚动到底部 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>
用的的两个工具函数
/** * @desc 函数防抖 * @param {需要防抖的函数} func * @param {延迟时间} wait */ export function debounce(func, wait = 500) { // 缓存一个定时器id let timer = 0; // 这里返回的函数是每次用户实际调用的防抖函数 // 如果已经设定过定时器了就清空上一次的定时器 // 开始一个新的定时器,延迟执行用户传入的方法 return function (...args) { if (timer) clearTimeout(timer) timer = setTimeout(() => { func.apply(this, args) }, wait) } } /** * @desc 是否滚到到容器底部 * @param {滚动容器} 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; }
总结
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