canvas绘制一个直角坐标系canvas绘制一个简单的直角坐标系、canvas canvas绘制一个简单的直角坐标系、

<!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>
  <style>
    canvas {
      display: block;
      margin: 10px auto;
      border: 2px solid green;
    }
  </style>
</head>

<body>
  <!-- canvas绘制直角坐标系 -->
  <canvas id="canvas" width="600" height="400">您的浏览器不支持canvas</canvas>
  <script>
    const canvas = document.getElementById('canvas')
    const ctx = canvas.getContext('2d')
    canvas.style.width = canvas.width + 'px'
    canvas.style.height = canvas.height + 'px'
    canvas.width = canvas.width * 2
    canvas.height = canvas.height * 2

    // 提前设置相关属性
    const ht = canvas.clientHeight
    const wd = canvas.clientWidth
    const pad = 20
    const bottomPad = 20
    const step = 100
    // 可以将以下代码封装成一个函数,传的参数就是上面的五个

    // 绘制坐标轴
    ctx.beginPath()
    ctx.lineWidth = 2
    ctx.strokeStyle = 'blue'
    ctx.moveTo(pad, pad)
    ctx.lineTo(pad, ht * 2 - bottomPad)
    ctx.lineTo(wd * 2 - bottomPad, ht * 2 - bottomPad)
    ctx.stroke()
    ctx.closePath()

    // 刻度  x轴
    ctx.beginPath()
    ctx.lineWidth = 2
    ctx.strokeStyle = 'blue'
    for (let i = 0; i < Math.floor(wd * 2 / step); i++) {
      ctx.moveTo(pad + i * step, ht * 2 - bottomPad)
      ctx.lineTo(pad + i * step, ht * 2 - bottomPad - 10)
    }
    ctx.stroke()
    ctx.closePath()
    // 刻度  y轴
    ctx.beginPath()
    ctx.lineWidth = 2
    ctx.strokeStyle = 'blue'
    for (let i = 0; i < Math.floor(ht * 2 / step); i++) {
      ctx.moveTo(pad, (ht * 2 - bottomPad) - i * step)
      ctx.lineTo(pad + 10, (ht * 2 - bottomPad) - i * step)
    }
    ctx.stroke()
    ctx.closePath()

  </script>
</body>

</html>