总结

通过canvas的captureStream属性返回的一个MediaStream对象，将生成的stream通过MediaRecorder对象生成录屏资源

const canvas_sun = require('./assets/canvas_sun.png')
const canvas_earth = require('./assets/canvas_earth.png')
const canvas_moon = require('./assets/canvas_moon.png')

function Draw () {
  const canvas = useRef();
  const recorder = useRef();
  const sun = new Image();
  const moon = new Image();
  const earth = new Image();

  const init = () => { 
    canvas.current = document.getElementById("canvas");
    sun.src = canvas_sun;
    moon.src =canvas_moon;
    earth.src = canvas_earth;
    window.requestAnimationFrame(draw);
  }


  const draw = () => { 
    const ctx = document.getElementById("canvas").getContext("2d");
    ctx.globalCompositeOperation = "destination-over";
    ctx.clearRect(0, 0, 300, 300); // 清除画布
    ctx.fillStyle = "rgb(0 0 0 / 40%)";
    ctx.strokeStyle = "rgb(0 153 255 / 40%)";
    ctx.save();
    ctx.translate(150, 150);

    // 地球
    const time = new Date();
    ctx.rotate(
      ((2 * Math.PI) / 60) * time.getSeconds() +
        ((2 * Math.PI) / 60000) * time.getMilliseconds(),
    );
    ctx.translate(105, 0);
    ctx.fillRect(0, -12, 40, 24); // 阴影
    ctx.drawImage(earth, -12, -12);

      // 月亮
      ctx.save();
      ctx.rotate(
        ((2 * Math.PI) / 6) * time.getSeconds() +
          ((2 * Math.PI) / 6000) * time.getMilliseconds(),
      );
      ctx.translate(0, 28.5);
      ctx.drawImage(moon, -3.5, -3.5);
      ctx.restore();

      ctx.restore();

      ctx.beginPath();
      ctx.arc(150, 150, 105, 0, Math.PI * 2, false); // 地球轨道
      ctx.stroke();

      ctx.drawImage(sun, 0, 0, 300, 300);

      window.requestAnimationFrame(draw);
  }

  const record = () => { 
    const stream = document.getElementById("canvas").captureStream();
    recorder.current = new MediaRecorder(stream, { mimeType: 'video/webm' });
    const data = [];
    recorder.current.ondataavailable = function (event) {
      console.log('event---record',event)
      if (event.data && event.data.size) {
        data.push(event.data);
      }
    };
    recorder.current.onstop = () => { 
      const url = URL.createObjectURL(new Blob(data, { type: 'video/webm' }));
      document.querySelector("#videoContainer").style.display = "block";
      document.querySelector("video").src = url;
    }

    recorder.current.start();
    setTimeout(() => { 
      recorder.current.stop();
    } ,6000)
  }

  useEffect(() => {
    init();
  }, []);
  
  useEffect(() => { 
    if (!canvas.current) { 
      return 
    }
    setTimeout(() => {
      record();
    }, 100);
  }, [canvas.current])


  return (
    <div>
      <canvas id="canvas" width="300" height="300"></canvas>
      <div id='videoContainer' style={{display:'none'}}>
      <video width="300"
           height="300"
           controls="true"
           autoplay="true"
           id="video"
           ></video>
      </div>
     </div>
  );
}