Canvas/10_canvas_三条折线_避免状态绘制陷阱.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')

      ctx.beginPath()
      ctx.moveTo(100, 100)
      ctx.lineTo(200, 150)
      ctx.lineTo(100, 200)
      ctx.lineWidth = 2
      ctx.strokeStyle = 'red'
      ctx.stroke()

      ctx.beginPath() // 使用beginPath告诉canvas绘制全新的路径，之前的状态不做保留，相当于跟之前的绘图状态做了一个隔离
      ctx.moveTo(300, 100)
      ctx.lineTo(400, 150)
      ctx.lineTo(300, 200)
      ctx.lineWidth = 3
      ctx.strokeStyle = 'green'
      ctx.stroke()

      ctx.beginPath()
      ctx.moveTo(500, 100)
      ctx.lineTo(600, 150)
      ctx.lineTo(500, 200)
      ctx.lineWidth = 4
      ctx.strokeStyle = 'blue'
      ctx.stroke()
    }

  </script>
</body>

</html>