React项目首页中用canvas实现星空

export default function initLoginBg(){
    var windowWidth = document.documentElement.clientWidth || document.body.clientWidth;
    var windowHeight = document.documentElement.clientHeight || document.body.clientHeight;
// var windowWidth = window.clientWidth;
// var windowHeight = window.clientHeight;
    var canvas = document.getElementById('canvas') as HTMLCanvasElement,
        ctx = canvas.getContext('2d') as CanvasRenderingContext2D,
        w = canvas.width = windowWidth,
        h = canvas.height = windowHeight,
        hue = 217,
        stars:IntStart[] = [],
        count = 0,
        maxStars = 500;//星星数量
    var canvas2 = document.createElement('canvas') ,
        ctx2 = canvas2.getContext('2d') as CanvasRenderingContext2D;
    canvas2.width = 100;
    canvas2.height = 100;
    var half = canvas2.width / 2,
        gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
    gradient2.addColorStop(0.025, '#CCC');
    gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
    gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
    gradient2.addColorStop(1, 'transparent');
    ctx2.fillStyle = gradient2;
    ctx2.beginPath();
    ctx2.arc(half, half, half, 0, Math.PI * 2);
    ctx2.fill();
// End cache
    function random(min:number, max=0) {
        if (arguments.length < 2) {
            max = min;
            min = 0;
        }
        if (min > max) {
            var hold = max;
            max = min;
            min = hold;
        }
        return Math.floor(Math.random() * (max - min + 1)) + min;
    }
    function maxOrbit(x:number, y:number) {
        var max = Math.max(x, y),
            diameter = Math.round(Math.sqrt(max * max + max * max));
        return diameter / 2;
//星星移动范围，值越大范围越小，
    }
    interface IntStart{
        orbitRadius:number;
        radius:number;
        orbitX:number;
        orbitY:number
        timePassed:number;
        speed:number;
        alpha:number;
        draw:()=>void;
    }
    var Star = function(this: IntStart) {
        this.orbitRadius = random(maxOrbit(w, h));
        this.radius = random(60, this.orbitRadius) / 18;
//星星大小
        this.orbitX = w / 2;
        this.orbitY = h / 2;
        this.timePassed = random(0, maxStars);
        this.speed = random(this.orbitRadius) / 500000;
//星星移动速度
        this.alpha = random(2, 10) / 10;
        count++;
        stars[count] = this;
    }
    Star.prototype.draw = function() {
        var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
            y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
            twinkle = random(10);
        if (twinkle === 1 && this.alpha > 0) {
            this.alpha -= 0.05;
        } else if (twinkle === 2 && this.alpha < 1) {
            this.alpha += 0.05;
        }
        ctx.globalAlpha = this.alpha;
        ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
        this.timePassed += this.speed;
    }
    for (var i = 0; i < maxStars; i++) {
        new Star.prototype.constructor();
    }
    function animation() {
        ctx.globalCompositeOperation = 'source-over';
        ctx.globalAlpha = 0.5; //尾巴
        ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';
        ctx.fillRect(0, 0, w, h)
        ctx.globalCompositeOperation = 'lighter';
        for (var i = 1, l = stars.length; i < l; i++) {
            stars[i].draw();
        };
        window.requestAnimationFrame(animation);
    }
    animation();
}

// 引入文件
import initLoginBg from "./init.ts";
import {useEffect} from "react";
const View = ()=>{
  // 加载完这个组件之后,加载背景
    useEffect(() => {
        initLoginBg()
        window.onresize = function () {
            initLoginBg()
        }
    }, [])
    return (
      <div>
      <canvas id="canvas" style={{display: "block"}}></canvas>
    </div>
    )
}