canvas绘制单个圆和同心圆

代码实现：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 1.设置canvas元素 -->
    <canvas id="canvas" width="200" height="200"></canvas>
    <script>
        //2.获取canvas画布
        const canvas =document.getElementById("canvas");
        //3.getContext()返回一个对象，对象包含绘制图形的方法和属性
        const ctx = canvas.getContext("2d");
        //arc(x,y,radius,startAngle,endAngle)
        ctx.arc(75,75,50,0,Math.PI*2);
        ctx.closePath();
        ctx.fillStyle="pink";
        ctx.fill();
        ctx.strokeStyle="#ff3d51"
        ctx.lineWidth =10;
        ctx.stroke();
    </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 1.设置canvas元素 -->
    <canvas id="canvas" width="400" height="400"></canvas>
    <script>
        //2.获取canvas画布
        const canvas =document.getElementById("canvas");
        //3.getContext()返回一个对象，对象包含绘制图形的方法和属性
        const ctx = canvas.getContext("2d");
        //第一个圆
        //arc(x,y,radius,startAngle,endAngle)
        ctx.beginPath();
        ctx.arc(200,200,100,0,Math.PI*2);
        ctx.closePath();
        ctx.fillStyle="red";
        ctx.fill();
        //第二个圆
        ctx.beginPath();
        ctx.arc(200,200,50,0,Math.PI*2);
        ctx.closePath();
        ctx.fillStyle ="gold"
        ctx.fill();
        
    </script>
</body>
</html>