JS實現視頻彈幕效果

使用ES6的模塊化開發及觀察者模式來實現。觀察者模式有很多種形式,這裡是使用“註冊—通知—撤銷註冊”的形式。TimeManager類可以返回一個單例,每一條彈幕作為一個觀察者,註冊到TimeManager類的單例的set表中,當單例的set中有數據時,被觀察者狀態被改變,執行動畫,並通知所有觀察者進行update狀態更新。彈幕移動超過視頻寬度時,從TimeManager中註銷。當TimeManager單例的set表中所有被觀察彈幕都註銷時,setInterval停止執行。

1、Bullet.js:

觀察者:實現彈幕樣式,和自身狀態更新update()方法.

2、TimeManager.js

被觀察者和Subject:可以增加和刪除觀察者對象,狀態改變時通知所有觀察者並更新狀態。

3、Player.js

播放器組件:簡單的播放器樣式,控制按鈕等都是默認樣式。。。

4、實現效果:

5、具體實現:

import TimeManager from './TimeManager.js';
 
export default class Bullet{
    
    elem;
    x;
    speedX=2;
    width;
 
    constructor(txt){
        this.elem = this.createElem(txt);
    }
    createElem(txt){
        if(this.elem) return
        let div = document.createElement("div");
        Object.assign(div.style,{
            position:"absolute",
            whiteSpace: "nowrap",
            fontSize:"16px",
            // color:"#000",
            color:"#e00",
        })
        div.textContent = txt;
        return div
    }
    appendTo(parent){
        if(typeof parent === "string") parent = document.querySelector(parent);
        parent.appendChild(this.elem);
        let rect = parent.getBoundingClientRect();
        this.elem.style.top = Math.random()*rect.height/4 +"px";
        this.width = this.elem.offsetWidth;
        this.x = rect.width;
        this.elem.style.left = this.x + "px";
        TimeManager.instance.add(this);
    }
    update(){
        if(!this.elem) return;
        this.x -= this.speedX;
        this.elem.style.left = this.x +"px";
        if(this.x<-this.width){
            this.elem.remove();
            TimeManager.instance.remove(this);
            this.elem = null;
        }
    }
}
export default class TimeManager{
    
    static _instance;
    list = new Set();
    ids;
 
    constructor(){
 
    }
    static get instance(){
        TimeManager._instance = TimeManager._instance? TimeManager._instance : new TimeManager();
        return TimeManager._instance;
    }
    add(elem){
        if(!elem) return
        if(elem.update) this.list.add(elem);
        if(!this.ids) this.ids = setInterval(()=>{
            this.update();
        },16);
    }
    remove(elem){
        if(!elem) return
        this.list.delete(elem);
        if(this.list.size===0 && this.ids){
            clearInterval(this.ids);
            this.ids=0;
        }
    }
    update(){
        this.list.forEach(item=>{
            item.update();
        })
    }
}
import Bullet from './Bullet.js';
 
export default class Player extends EventTarget{
 
    static WIDTH=638;
    static HEIGHT=493;
    elem;
    input;
 
    constructor(path){
        super();
        this.elem = this.createElem(path);
        document.addEventListener("keyup",e=>this.keyHandler(e));
    }
    keyHandler(e){
        if(e.keyCode !== 13) return;
        if(this.input.value.trim().length===0) return;
        let b = new Bullet(this.input.value);
        b.appendTo(this.elem);
        this.input.value = "";
    }
    appendTo(parent){
        if(typeof parent==="string") parent = document.querySelector(parent);
        parent.appendChild(this.elem);
    }
    createElem(path){
        // 播放器最外層容器
        let player = document.createElement("div");
        player.className = "player";
        Object.assign(player.style,{
            width:Player.WIDTH+"px",
            height:Player.HEIGHT+"px",
            userSelect:"none",
            overflow: "hidden",
            position:"relative",
            verticalAlign:"baseline",
        })
        // 播放器視頻播放部分:應包括頂部作者和反饋欄、視頻狀態按鈕、視頻展示部分。。。。
        let videoWrap = document.createElement("div");
        Object.assign(videoWrap.style,{
            width:"100%",
            height:"447px",
            backgroundColor:"#000",
            position:"relative",
            top:0,
            display:"flex",
            flexDirection:"column",
        })
        // 創建播放器上層:包括標題,作者,反饋意見和舉報等。。。。
        let videoTop = document.createElement("div");
        Object.assign(videoTop.style,{
            width:"100%",
            height:"42px",
            position:"relative",
            top:"0px",
            left:"0px",
            opacity:"0",
            color:"#fff",
            pointerEvents:"none",
            // transition: "all .2s ease-in-out",
            transition: "all .2s",
        })
        // 視頻播放狀態開關
        // let videoState = document.createElement("div");
        // 視頻播放部分
        let videoContent = document.createElement("div");
        Object.assign(videoContent.style,{
            width:"100%",
            // height:"100%",
            height:"361px",
            position:"relative",
            userSelect:"none",
        })
        let video = document.createElement("video");
        video.src = path;
        video.controls = "controls";
        video.preload = "auto";
        Object.assign(video.style,{
            // 視頻居中:進度條被拉長,但是視頻不會被拉長,直接居中:
            height:"100%",
            width:"100%",
        })
        videoContent.appendChild(video);
 
        // 視頻播放和彈幕滾動控制欄:清晰度/倍速/循環/鏡像/寬屏/網頁全屏/進度條等、、、、、
        let videoControlWrap = document.createElement("div");
        Object.assign(videoControlWrap.style,{
            width:"100%",
            height:"44px",
            opacity:"0",
            position:"relative",
            bottom:"0",
        })
 
        // 底部發送彈幕及設置發送彈幕樣式:例如彈幕顏色/字號/滾動/懸停/速度/字體/屏蔽等。。。
        let bottomArea = document.createElement("div");
        Object.assign(bottomArea.style,{
            width:"100%",
            height:"46px",
        })
        this.input = document.createElement("input");
        Object.assign(this.input.style,{
            width:"130px",
            height:"30px",
            color:"#212121",
            // border:"0px",
            lineHeight:"30px",
            boxSizing: "border-box",
            minWidth: "115px",
            padding:"0 5px",
            fontSize:"12px",
            border:"1px solid #e7e7e7",    //外框樣式:
            backgroundColor:"#f4f4f4",
        })
        bottomArea.appendChild(this.input);
 
        videoWrap.appendChild(videoTop);
        videoWrap.appendChild(videoContent);
        videoWrap.appendChild(videoControlWrap);
 
        player.appendChild(videoWrap);
        player.appendChild(bottomArea);
        return player;
    }
}
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
    </style>
</head>
<body>
    <script type="module">
        import Player from './js/Player.js';
        import TimeManager from './js/TimeManager.js';
        import Bullet from './js/Bullet.js';
 
        // 播放器使用
        let player = new Player("./test3.mp4");
        player.appendTo("body");
 
    </script>
</body>
</html>

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