使用HTML5 Canvas绘制动态时钟的JavaScript实现

核心代码解析

var canvas = document.getElementById("clock");
var clock = canvas.getContext("2d");
 
function zhong() {
 clock.save();
 //开始画外层圆
 clock.translate(200, 200);
 clock.strokeStyle = 'black';
 clock.lineWidth = 3;
 clock.beginPath();
 clock.arc(0, 0, 195, 0, 2 * Math.PI);
 clock.stroke();

 //时钟上的数字
 var shuzi = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2];
 clock.font = "30px Arial";
 clock.textAlign = "center";
 clock.textBaseline = "middle";
 shuzi.forEach(function(number, i) {
 var rad = 2 * Math.PI / 12 * i;
 var x = Math.cos(rad) * 180;
 var y = Math.sin(rad) * 180;
 clock.fillText(number, x, y);
 });

 // 小圆点

 for(j = 0; j < 60; j++) {
 var h = 2 * Math.PI / 60 * j;
 var m = Math.cos(h) * 180;
 var n = Math.sin(h) * 180;
 clock.fillStyle = 'black';
 clock.beginPath();
 if(j % 5 === 0) {
 continue;
 }
 clock.arc(m, n, 3, 0, 2 * Math.PI);
 clock.fill();
 }
}
function drawHour(hour,min) {
 clock.save();
 var rad = 2 * Math.PI / 12 * hour;
 var red = 2 *Math.PI/12/60*min;
 clock.rotate(rad+red);
 clock.lineWidth = 10;
 clock.lineCap = "round";
 clock.beginPath();
 clock.moveTo(0, 5);
 clock.lineTo(0, -100);
 clock.stroke();
 clock.restore();
}

function drawmin(min) {
 clock.save();
 var rad = 2 * Math.PI / 60 * min;
 clock.rotate(rad);
 clock.lineWidth = 5;
 clock.lineCap = "round";
 clock.beginPath();
 clock.moveTo(0, 10);
 clock.lineTo(0, -150);
 clock.stroke();
 clock.restore();
}

function drawsec(sec) {
 clock.save();
 var rad = 2 * Math.PI / 60 * sec;
 clock.rotate(rad);
 clock.lineWidth = 2;
 clock.lineCap = "round";
 clock.strokeStyle = "red";
 clock.beginPath();
 clock.moveTo(0, 10);
 clock.lineTo(0, -180);
 clock.stroke();
 clock.restore();
}

function dian() {
 clock.fillStyle = "white";
 clock.beginPath();
 clock.arc(0, 0, 2, 0, 2 * Math.PI);
 clock.fill();
}

function xuanzhuan() {
 clock.clearRect(0,0,400,400);
 zhong();
 var now = new Date();
 var hour = now.getHours();
 var min = now.getMinutes();
 var sec = now.getSeconds();
 drawHour(hour,min);
 drawmin(min);
 drawsec(sec);
 dian();
 clock.restore();
}
xuanzhuan();

setInterval(xuanzhuan, 1000);