绘制一个矩形。请用红色的笔触颜色

<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">

您的浏览器不支持 HTML5 canvas 标签。</canvas>

<script>

  var c = document.getElementById("myCanvas");

  var ctx = c.getContext("2d");

  ctx.strokeStyle = "#FF0000";

  ctx.strokeRect(20, 20, 150, 100);

</script>