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

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"

});

}

}

};

*{

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;

}

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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