Canvas et JS implémentent une animation d'horloge dynamique

nbsp;html>


  <meta>
  <title>canvas时钟</title>
  <style>
    canvas {
      border: 1px solid red;
    }
  </style>


<canvas></canvas>

<script>
  function Clock(opt) {
    for (var key in opt) {
      this[key] = opt[key];
    }
    this.init();
  }
  Clock.prototype = {
    init: function () {
      var self = this;
      var ctx = this.ctx;
      this.timer = setInterval(function(){
        ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height);
        self.drawDial();
        self.drawDegreeScale();
        self.drawNumber();
        self.drawPointers();
      },1000);
    },
    drawDial: function () {
      var ctx = this.ctx;
      ctx.save();
      ctx.beginPath();
      ctx.lineWidth = this.clockDialW;
      ctx.strokeStyle = this.clockDialColor;
      ctx.arc(this.clockX, this.clockY, this.clockRadius, 0, 2 * Math.PI);
      ctx.stroke();
      ctx.restore();
    },
    drawDegreeScale: function () {
      var ctx = this.ctx;
      var clockRadius = this.clockRadius;
      var clockX = this.clockX;
      var clockY = this.clockY;
      var bigDegreeScaleL = this.bigDegreeScaleL;
      var smallDegreeScale = this.smallDegreeScale;
      var startX, startY, endX, endY, radian;
      ctx.save();
      for (var i = 0; i < 12; i++) {
        radian = i * Math.PI / 6;
        endX = clockX + clockRadius * Math.cos(radian);
        endY = clockY + clockRadius * Math.sin(radian);
        if (radian % (Math.PI / 2) == 0) {
          startX = clockX + (clockRadius - bigDegreeScaleL) * Math.cos(radian);
          startY = clockY + (clockRadius - bigDegreeScaleL) * Math.sin(radian);
          ctx.lineWidth = this.bigDCWidth;
        } else {
          startX = clockX + (clockRadius - smallDegreeScale) * Math.cos(radian);
          startY = clockY + (clockRadius - smallDegreeScale) * Math.sin(radian);
          ctx.lineWidth = this.smallDCWidth;
        }
        ctx.beginPath();
        ctx.moveTo(startX, startY);
        ctx.lineTo(endX, endY);
        ctx.stroke();
        ctx.restore();
      }
    },
    drawNumber: function () {
      var ctx = this.ctx;
      var textX, textY, textRadian;
      var clockX = this.clockX;
      var clockY = this.clockY;
      var clockRadius = this.clockRadius;
      ctx.font = &#39;20px 微软雅黑&#39;;
      ctx.fillStyle = &#39;red&#39;;
      ctx.textAlign = &#39;center&#39;;
      ctx.textBaseline = &#39;middle&#39;;
      ctx.save();
      for (var i = 0; i < 12; i++) {
        textRadian = i * Math.PI / 6 - Math.PI/3;
        textX = clockX + (clockRadius - 40) * Math.cos(textRadian);
        textY = clockY + (clockRadius - 40) * Math.sin(textRadian);
        ctx.beginPath();
        ctx.fillText(i + 1, textX, textY);
      }
      ctx.restore();
    },
    drawPointers: function () {
      var date = new Date();
      var h = date.getHours();
      var m = date.getMinutes();
      var s = date.getSeconds();
      h = h % 12;
      var hRadian = 2 * Math.PI / 12 * h - Math.PI / 2;
      this.drawPoint(hRadian,30,&#39;red&#39;,8);
      var mRadian = 2 * Math.PI / 60 * m - Math.PI / 2;
      this.drawPoint(mRadian,50,&#39;blue&#39;,6);
      var sRadian = 2 * Math.PI / 60 * s - Math.PI / 2;
      this.drawPoint(sRadian,70,&#39;green&#39;,2);
    },
    drawPoint: function (radian, length,color,lineWidth) {
      var x = this.clockX + Math.cos(radian) * length;
      var y = this.clockY + Math.sin(radian) * length;
      var ctx = this.ctx;
      ctx.save();
      ctx.beginPath();
      ctx.strokeStyle = color;
      ctx.lineWidth = lineWidth;
      ctx.moveTo(this.clockX,this.clockY);
      ctx.lineTo(x,y);
      ctx.stroke();
      ctx.restore();
    }
  };
</script>
<script>
  var canvas = document.querySelector(&#39;canvas&#39;);
  var ctx = canvas.getContext(&#39;2d&#39;);
  var clock = new Clock({
    ctx: this.ctx,
    clockRadius: 150,
    clockX: 300,
    clockY: 300,
    clockDialW: 6,
    clockDialColor: &#39;blue&#39;,
    bigDegreeScaleL: 20,
    bigDCWidth: 6,
    smallDegreeScale: 10,
    smallDCWidth: 4
  });
</script>