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canvas制作动态时钟效果

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JavaScript

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>canvas clock</title>
  <style media="screen">
    div{text-align:center;margin-top:250px;}
  </style>
</head>
<body>
<div>
  <canvas id="clock" width="600" height="600"></canvas>
</div>
<script type="text/javascript">
var dom = document.getElementById("clock");
var ctx = dom.getContext('2d');
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
var rem = width / 200;

function drawBackground(){
  ctx.save();
  ctx.translate(r,r);
  ctx.beginPath();
  ctx.lineWidth = 10 * rem;
  ctx.arc(0,0,r-ctx.lineWidth / 2,0,2*Math.PI,false);
  ctx.stroke();

  var hourNumbers = [3,4,5,6,7,8,9,10,11,12,1,2];
  ctx.font = 18 * rem + 'px Arial';
  ctx.textAlign = 'center';
  ctx.textBaseline = 'middle';
  hourNumbers.forEach(function(number, i){
    var rad = 2 * Math.PI / 12 * i;
    var x = Math.cos(rad) * (r - 30 * rem);
    var y = Math.sin(rad) * (r - 30 * rem);
    ctx.fillText(number, x, y)
  });

  for (var i = 0; i < 60; i++) {
    var rad = 2 * Math.PI / 60 *i;
    var x = Math.cos(rad) * (r - 18 * rem);
    var y = Math.sin(rad) * (r - 18 * rem);
    ctx.beginPath();
    if (i % 5 === 0) {
      ctx.fillStyle = "#000";
      ctx.arc(x, y, 2 * rem, 0, 2 * Math.PI, false);
    }else{
      ctx.fillStyle = "#ccc";
      ctx.arc(x, y, 2 * rem, 0, 2 * Math.PI, false);
    }
    ctx.fill();
  };
}

function drawHour(hour, minute){
  ctx.save();
  ctx.beginPath();
  var rad = 2 * Math.PI / 12 * hour;
  var mrad = 2 * Math.PI / 12 / 60 * minute;
  ctx.rotate(rad + mrad);
  ctx.lineWidth = 6 * rem;
  ctx.lineCap = 'round';
  ctx.moveTo(0, 10);
  ctx.lineTo(0, -r / 2);
  ctx.stroke();
  ctx.restore();
}

function drawMinute(minute){
  ctx.save();
  ctx.beginPath();
  var rad = 2 * Math.PI / 60 * minute;
  ctx.rotate(rad);
  ctx.lineWidth = 3 * rem;
  ctx.lineCap = 'round';
  ctx.moveTo(0, 10 * rem);
  ctx.lineTo(0, -r + 30 * rem);
  ctx.stroke();
  ctx.restore();
}

function drawSecond(second){
  ctx.save();
  ctx.beginPath();
  ctx.fillStyle = '#c14543';
  var rad = 2 * Math.PI / 60 * second;
  ctx.rotate(rad);
  ctx.moveTo(-2, 20 * rem);
  ctx.lineTo(2, 20 * rem);
  ctx.lineTo(1, -r + 18 * rem);
  ctx.lineTo(-1, -r + 18 * rem)
  ctx.fill();
  ctx.restore();
}

function drawDot(){
  ctx.beginPath();
  ctx.fillStyle = '#fff';
  ctx.arc(0, 0, 3 * rem, 0, 2 * Math.PI, false);
  ctx.fill();
}

function draw(){
  ctx.clearRect(0,0,width,height);
  var now = new Date();
  var hour = now.getHours();
  var minute = now.getMinutes();
  var second = now.getSeconds();
  drawBackground();
  drawHour(hour, minute);
  drawMinute(minute);
  drawSecond(second);
  drawDot();
  ctx.restore();
}

draw();
setInterval(draw, 1000);
</script>
</body>
</html>

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