美丽的时钟

案例绘制一个时钟

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>美丽的时钟</title>
		<script language="javascript">
			window.onload=function(){
			var clock=document.getElementById("clock");
			var cxt=clock.getContext("2d");
			
			function circle(r,color,w){
				cxt.lineWidth=w;//设置线条宽度
				cxt.strokeStyle=color;//设置线条颜色
				cxt.beginPath();//起始一条路径
				cxt.arc(250,250,r,0,360,false);//绘制曲线，圆心坐标为画布中心
				cxt.stroke();//绘制已定义的路径
			}
			function line(i){
				cxt.save();
				cxt.strokeStyle="#000";
				cxt.translate(250,250);
				cxt.rotate(i*6*Math.PI/180);
				cxt.beginPath();
				if(i%5==0){
					cxt.lineWidth=7;
					cxt.moveTo(0,-170);
				}else{
					cxt.lineWidth=5;
					cxt.moveTo(0,-180);
				}
				cxt.lineTo(0,-190);
				cxt.stroke();
				cxt.restore();
			}
			
			function needle(color,w,s,t,r){
				cxt.save();
				cxt.strokeStyle=color;
				cxt.lineWidth=w;
				cxt.translate(250,250);
				cxt.rotate(r*Math.PI/180);
				cxt.beginPath();
				cxt.moveTo(0,s);
				cxt.lineTo(0,t);
				cxt.stroke();
				cxt.restore();	
			}
			function preSec(r){
				cxt.save();
				cxt.lineWidth=2;
				cxt.strokeStyle="red";
				cxt.translate(250,250);
				cxt.rotate(r*Math.PI/180);
				cxt.beginPath();
				cxt.arc(0,-150,3,0,360,false);
				cxt.fillStyle="#808080";
				cxt.fill();
				cxt.stroke();
				cxt.restore();
			}
			function drawPoint(){
				var now =new Date();
				var h=now.getHours();
				h=h>12?h-12:h;
				var min=now.getMinutes();
				var sec=now.getSeconds();
				needle("#000",10,20,-60,(h*30+min/60*30));
				needle("#808080",6,30,-90,min*6);
				needle("red",2,35,-180,sec*6);
				preSec(sec*6);
			}
			function draw(){
				cxt.clearRect(0,0,500,500);
				circle(200,"blue",7);
				for(var i=0;i<60;i++){
					line(i);
				}
				drawPoint();
				circle(10,"red",2);
				circle(3,"red",3);
			}
			setInterval(function(){
				draw();
			},1000);
			}
				</script>	
	</head>
	<body>
		<canvas width="500" height="500" id="clock">
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	</body>
</html>