为了秒钟匀速转动，缩小秒钟移动的弧度，加快时间间隔，为什么秒钟还是一秒动一下。
var dom = document.getElementById('clock');
var ctx = dom.getContext('2d');
console.log(ctx);
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
var rem = width / 200;
function drawBackground() {
ctx.save();
//坐标定义在中间
ctx.translate(r,r);
//起始一条路径
ctx.beginPath();
//路径宽度
ctx.lineWidth = 10 * rem;
// 创建弧或曲线()
ctx.arc(0,0,r - ctx.lineWidth / 2,0,2*Math.PI, false);
//绘制已定义的路径
ctx.stroke();
// 定义小时数
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';
// 遍历小时数，获取坐标
hourNumbers.forEach(function(number, i) {
//获取弧度
var rad = 2 * Math.PI / 12 * i;
// 坐标
var x = Math.cos(rad) * (r - 30 * rem);
var y = Math.sin(rad) * (r - 30 * rem);
// 文本填充
ctx.fillText(number, x, y);
});
//遍历60个点
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);
// 重置外圆的绘制
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);
}
// 填充圆点
ctx.fill();
}
}
function drawHour(hour,minute) {
ctx.save();
ctx.beginPath();
ctx.lineWidth = 6 * rem;
ctx.lineCap = 'round';
var rad = 2 * Math.PI / 12* hour;
var mrad = 2 * Math.PI / 12 / 60 * minute;
ctx.rotate(rad + mrad);
// 画线位置
ctx.moveTo(0 * rem ,10);
ctx.lineTo(0 * rem, -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 = "#f00";
var rad = 2 * Math.PI / 1200 * second;
ctx.rotate(rad);
ctx.moveTo(-2 * rem ,20 * rem);
ctx.lineTo(2 * rem, 20 * rem);
ctx.lineTo(1 * rem, -r +18 * rem);
ctx.lineTo(-1 * rem, -r +18 * rem);
ctx.fill();
ctx.restore();
}
function drawDot(){
ctx.beginPath();
ctx.fillStyle = "#fff";
ctx.arc(0,0,3,0,2*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();
console.log(hour,minute,second);
}
setInterval(draw,50);
