(编辑:jimmy 日期: 2024/12/23 浏览:2)
前言
如今几乎所有的视频网站都有弹幕功能,那么今天我们就自己用原生 JavaScript 封装一个弹幕类。这个类希望有如下属性和实例方法:
属性
方法
PS:有一些自封装的工具函数就不贴出来了,大概知道意思就好
初始化
引入JavaScript文件之后,我们希望如下使用,先采取默认配置。
let barrage = new Barrage({ el: '#container' })
参数初始化:
function Barrage(options) { let { el, height, mode, speed, gapWidth, } = options this.container = document.querySelector(el) this.height = height || 30 this.speed = speed || 15000 //2000ms this.gapWidth = gapWidth || 20 this.list = [] this.mode = mode || 'half' this.boxSize = getBoxSize(this.container) this.perSpeed = Math.round(this.boxSize.width / this.speed) this.rows = initRows(this.boxSize, this.mode, this.height) this.timeoutFuncs = [] this.indexs = [] this.idMap = [] }
先接受好参数然后初始化,下面看看getBoxSize和initRows
function getBoxSize(box) { let { height, width } = window.getComputedStyle(box) return { height: px2num(height), width: px2num(width) } function px2num(str) { return Number(str.substring(0, str.indexOf('p'))) } }
通过getComputedStyleapi计算出盒子的宽高,这里用来计算容器的宽高,之后也会用到。
function initRows(box, mode, height) { let divisor = getDivisor(mode) rows = Math.ceil(box.height * divisor / height) return rows } function getDivisor(mode) { let divisor = .5 switch (mode) { case 'half': divisor = .5 break case 'top': divisor = 1 / 3 break; case 'full': divisor = 1; break default: break; } return divisor }
根据高度算出弹幕应该有多少行,下面会有地方用到行数。
插入数据
有两种插入数据的方法,一种是添加源数据,一种是持续添加。先来看添加源数据的方法:
this.pushData = function (data) { this.initDom() if (getType(data) == '[object Object]') { //插入单条 this.pushOne(data) } if (getType(data) == '[object Array]') { //插入多条 this.pushArr(data) } }
this.initDom = function () { if (!document.querySelector(`${el} .barrage-list`)) { //注册dom节点 for (let i = 0; i < this.rows; i++) { let div = document.createElement('div') div.classList = `barrage-list barrage-list-${i}` div.style.height = `${this.boxSize.height*getDivisor(this.mode)/this.rows}px` this.container.appendChild(div) } } } this.pushOne = function (data) { for (let i = 0; i < this.rows; i++) { if (!this.list[i]) this.list[i] = [] } let leastRow = getLeastRow(this.list) //获取弹幕列表中最少的那一列,弹幕列表是一个二维数组 this.list[leastRow].push(data) } this.pushArr = function (data) { let list = sliceRowList(this.rows, data) list.forEach((item, index) => { if (this.list[index]) { this.list[index] = this.list[index].concat(...item) } else { this.list[index] = item } }) } //根据行数把一维的弹幕list切分成rows行的二维数组 function sliceRowList(rows, list) { let sliceList = [], perNum = Math.round(list.length / rows) for (let i = 0; i < rows; i++) { let arr = [] if (i == rows - 1) { arr = list.slice(i * perNum) } else { i == 0 "htmlcode">this.addData = function (data) { this.pushData(data) this.start() }发射弹幕
下面来看看发射弹幕的逻辑
this.start = function () { //开始调度list this.dispatchList(this.list) } this.dispatchList = function (list) { for (let i = 0; i < list.length; i++) { this.dispatchRow(list[i], i) } } this.dispatchRow = function (row, i) { if (!this.indexs[i] && this.indexs[i] !== 0) { this.indexs[i] = 0 } //真正的调度从这里开始,用一个实例变量存储好当前调度的下标。 if (row[this.indexs[i]]) { this.dispatchItem(row[this.indexs[i]], i, this.indexs[i]) } }this.dispatchItem = function (item, i) { //调度过一次的某条弹幕下一次在调度就不需要了 if (!item || this.idMap[item.id]) { return } let index = this.indexs[i] this.idMap[item.id] = item.id let div = document.createElement('div'), parent = document.querySelector(`${el} .barrage-list-${i}`), width, pastTime div.innerHTML = item.content div.className = 'barrage-item' parent.appendChild(div) width = getBoxSize(div).width div.style = `width:${width}px;display:none` pastTime = this.computeTime(width) //计算出下一条弹幕应该出现的时间 //弹幕飞一会~ this.run(div) if (index > this.list[i].length - 1) { return } let len = this.timeoutFuncs.length //记录好定时器,后面清空 this.timeoutFuncs[len] = setTimeout(() => { this.indexs[i] = index + 1 //递归调用下一条 this.dispatchItem(this.list[i][index + 1], i, index + 1) }, pastTime); }//用css动画,整体还是比较流畅的 this.run = function (item) { item.classList += ' running' item.style.left = "left:100%" item.style.display = '' item.style.animation = `run ${this.speed/1000}s linear` //已完成的打一个标记 setTimeout(() => { item.classList+=' done' }, this.speed); } //根据弹幕的宽度和gapWth,算出下一条弹幕应该出现的时间 this.computeTime = function (width) { let length = width + this.gapWidth let time = Math.round(length / this.boxSize.width * this.speed/2) return time }动画css具体如下
@keyframes run { 0% { left: 100%; } 50% { left: 0 } 100% { left: -100%; } } .run { animation-name: run; }其余方法
停止
利用动画的paused属性停止
this.stop = function () { let items = document.querySelectorAll(`${el} .barrage-item`); [...items].forEach(item => { item.className += ' pause' }) }.pause { animation-play-state: paused !important; }重新开始
移除pause类即可
this.restart = function () { let items = document.querySelectorAll(`${el} .barrage-item`); [...items].forEach(item => { removeClassName(item, 'pause') }) }打开关闭
做一个显示隐藏的逻辑即可
this.close = function () { this.container.style.display = 'none' } this.open = function () { this.container.style.display = '' }清理弹幕
this.clearData = function () { //清除list this.list = [] //清除dom document.querySelector(`${el}`).innerHTML = '' //清除timeout this.timeoutFuncs.forEach(fun => clearTimeout(fun)) }最后用一个定时器定时清理过期的弹幕:
setInterval(() => { let items = document.querySelectorAll(`${el} .done`); [...items].forEach(item=>{ item.parentNode.removeChild(item) }) }, this.speed*5);最后
感觉这个的实现还是有缺陷的,如果是你设计这么一个类,你会怎么设计呢?