html5 canvas clock 时钟效果

html：

js:

var dom = document.getElementById('canvas');
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.strokeStyle = '#42ca78';
	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.fillStyle = '#fff'
	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 = '#f16192';
			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 * rem);
	ctx.lineTo(0, -r / 2 );
	ctx.stroke();
	ctx.restore();
}


function drawMinute(minute,second){
	ctx.save();
	ctx.beginPath();
	var rad = 2*Math.PI / 60 * minute;
	var mrad = 2*Math.PI / 60 / 60 * second;
	ctx.rotate(rad + mrad);
	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 = '#f16192'
	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,second);
	drawSecond(second);
	drawDot();
	ctx.restore();
}


draw()
setInterval(draw,1000);

效果图：