背景の星空をCanvasで描画する

const canvas = canvasRef.current;
const ctx = canvas.getContext("2d");
const frameId:number;
const animate = ()=>{
  //以下描画勝利
  ctx.clearReact(0,0,canvas.width,canvas.height);
  ctx.beginPath();
  ctx.arc(star.x, star.y, star.size, 0, Math.PI * 2);
  ctx.fillStyle = `rgba(255, 255, 255, ${star.alpha})`;
  ctx.shadowBlur = star.size > 1.2 ? 4 : 0;
  ctx.shadowColor = 'rgba(255, 255, 255, 0.8)';
  ctx.fill();
  //callbackでまた呼出し
  frameId = requestAnimationFrame(animate);
}
//初回の呼出し
requestAnimationFrame(animate)

//ページを離れるときに
cancelAnimationFrame(frameId);