canvas 模拟时钟

<meta charset="utf-8">
<canvas width="1000" height="1000" id="clockCanvas" style="border:1px solid red;">
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</canvas>
<script>
    var clockID = document.getElementById("clockCanvas");
    var clock = clockID.getContext("2d");
            function drawClock(id){
                //*每次清空画布(在给定矩形内清空一个矩形：)
                    clock.clearRect(0,0,1000,1000);
                //获取系统当前时间（时 、分 、秒）
                    var now = new Date();
                    var sec = now.getSeconds();
                    var mins = now.getMinutes();
                    var hours = now.getHours();
                //绘制文字，显示系统当前时间：
                    clock.save();   //*保存之前状态
                        clock.translate(0,500);  //*更换原点(0,0)位置为(0,500)
                        clock.fillStyle = "#f00";
                        clock.strokeStyle = "#eee";
                        clock.font = "bold 20px 微软雅黑";
                        clock.strokeText("系统当前时间为："
                            +hours+"时"
                            +mins+"分"
                            +sec+"秒", 100, 100);
                        clock.fillText("系统当前时间为："
                            +hours+"时"
                            +mins+"分"
                            +sec+"秒", 100, 100);  //*在画布上输出的文本及位置
                    clock.restore();
                //计算：满60分加一小时
                    hours = hours + mins/60;
                //计算：将24小时制转化为12小时制
                    hours = hours>12?hours-12:hours;
                //1.画表盘
                    clock.beginPath();
                    clock.lineWidth = 10;
                    clock.strokeStyle = "#ff00ff";
                    clock.arc(300, 300, 200, 0, 360, false);
                    clock.stroke();
                    clock.closePath();
                //2.画刻度盘
                    //2.1 时刻度
                    for(var i = 0; i < 12; i++){
                        clock.save();
                        //将起始点定位到圆心
                            clock.translate(300,300);
                        //设置刻度的样式
                            clock.lineWidth = 7;
                            clock.strokeStyle = "#999999";
                        //设置旋转角度
                            clock.rotate(i*30*Math.PI/180);
                            clock.beginPath();
                            clock.moveTo(0, -170);
                            clock.lineTo(0, -190);
                            clock.font = "normal 20px impack";
                            clock.textAlign = "left";
                            clock.textBaseLine = "top";
                            clock.strokeText(i, i*(-50)*Math.PI/180, -150);
                            clock.closePath();
                        //画刻度线
                            clock.stroke();
                            clock.restore();
                    }
                    //2.2 分刻度
                    for(var j = 0; j<60; j++){
                        clock.save();
                        //设置起始点坐标
                            clock.translate(300,300);
                            clock.lineWidth = 5;
                            clock.strokeStyle = "#999999";
                        //设置旋转角度
                            clock.rotate(j*6*Math.PI/180);
                            clock.beginPath();
                            clock.moveTo(0, -180);
                            clock.lineTo(0, -190);
                            clock.closePath();
                            clock.stroke();
                            clock.restore();
                    }
                //3.1 时针
                     clock.save();
                     clock.translate(300,300);
                     clock.lineWidth = 7;
                     clock.strokeStyle = "#000000";
                     //设置小时的旋转角度，没转一次走30°
                     clock.rotate(hours*30*Math.PI/180);
                     clock.beginPath();
                     clock.moveTo(0,15);
                     clock.lineTo(0,-120);
                     clock.stroke();
                     clock.closePath();
                     clock.restore();
                //3.2 分针
                    clock.save();
                    clock.translate(300, 300);
                    clock.rotate(mins*6*Math.PI/180);
                    clock.lineWidth = 5;
                    clock.strokeStyle = "#000";
                    clock.beginPath();
                    clock.moveTo(0,20);
                    clock.lineTo(0,-160);
                    clock.stroke();
                    clock.closePath();
                    clock.restore();
                //3.3 秒针
                    clock.save();
                    clock.translate(300,300);
                    clock.rotate(sec*6*Math.PI/180);
                    clock.lineWidth = 3;
                    clock.strokeStyle = "#f00";
                    clock.beginPath();
                    clock.moveTo(0, 25);
                    clock.lineTo(0,-165);
                    clock.stroke();
                    clock.closePath();
                //3.3.1 秒针圆心处一个小圈
                    clock.fillStyle = "#999";
                    clock.strokeStyle = "#f00";
                    clock.beginPath();
                    clock.arc(0,0,6,0,360,false);
                    clock.fill();
                    clock.stroke();
                    clock.closePath();
                //3.秒针顶部一个小圈
                    clock.beginPath();
                    clock.arc(0,-140,6,0,360,false);
                    clock.fill();
                    clock.stroke();
                    clock.closePath();
                    clock.restore();
            };
            drawClock();
            setInterval(drawClock,1000);
</script>