用canvas画个矩形
<!DOCTYPE html>
<html>
<body>
<canvas id="my-canvas"></canvas>
<script type="text/javascript">
// 画个矩形
const canvas = document.getElementById('my-canvas');
const ctx = canvas.getContext('2d');
ctx.fillStyle = '#ff0000';
ctx.fillRect(0, 0, 80, 100);
</script>
</body>
</html>