Canvas/05_canvas_多个圆弧.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>Page Title</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>

<body>
  <canvas id="myCanvas" style="border:1px solid red;">
    当前浏览器不支持canvas，请更换浏览器后再试
  </canvas>
  <script>
    window.onload = function () {
      var canvas = document.getElementById('myCanvas')

      canvas.width = 800
      canvas.height = 800

      var ctx = canvas.getContext('2d')

      for (var i = 0; i < 10; i++) {
        ctx.beginPath()
        // * 顺势针画
        ctx.arc(50 + i * 100, 60, 40, 0, 2 * Math.PI * (i + 1) / 10)
        ctx.stroke()
      }

      for (var i = 0; i < 10; i++) {
        ctx.beginPath()
        // * 逆时针画
        ctx.arc(50 + i * 100, 150, 40, 0, 2 * Math.PI * (i + 1) / 10, true)
        ctx.stroke()
      }

      for (var i = 0; i < 10; i++) {
        ctx.beginPath()
        ctx.arc(50 + i * 100, 240, 40, 0, 2 * Math.PI * (i + 1) / 10)
        // * 关闭路径
        ctx.closePath()
        ctx.stroke()
      }

      for (var i = 0; i < 10; i++) {
        ctx.beginPath()
        ctx.arc(50 + i * 100, 330, 40, 0, 2 * Math.PI * (i + 1) / 10)
        // * 关闭路径
        ctx.closePath()
        ctx.fill()
      }

      for (var i = 0; i < 10; i++) {
        ctx.beginPath()
        ctx.arc(50 + i * 100, 420, 40, 0, 2 * Math.PI * (i + 1) / 10)
        // * 不关闭路径
        // ctx.closePath()
        // * 结果和上面一个一样，说明closePath对fill没用，仅对路径绘制有效果
        // * 调用fill，会自动帮你closePath
        ctx.fill()
      }

    }
  </script>
</body>

</html>