有经常看直播的小伙伴们应该都有发现，我们在打开一个直播间之后评论会一直不断的滚动一会就跳过我们刚看到的那部分，我们就需要自己手动往上翻才可以找到我们要的刚才的评论，那么今天我们就来说说有关于：“在html5中怎么设置直播间评论滚动？”这个问题的相关内容吧！

首先我们来看看效果图：

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

通过这篇文章的分析想必大家对于：“在html5中怎么设置直播间评论滚动？”这方面的相关内容也有了不少的了解，当然了如果你对于html5这方面的知识内容有感兴趣的小伙伴也可以在W3Cschool中进行学习和了解！