JS 第三方工具封裝經典案例（canvas時鐘）

2b勿擾發表於2020-01-21
JS封裝Canvas
<!DOCTYPE html>
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <title>走動的時鐘</title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link rel="stylesheet" href="">
    </head>
    <body>
            <canvas id="canvas" width='500' height="500"></canvas>
   <script>
   window.onload = function(){
    function clock(){
        var now = new Date();
        var ctx = document.getElementById('canvas').getContext('2d');
        ctx.save();
        ctx.clearRect(0,0,150,150);
        //統一樣式設定
        ctx.translate(75,75);
        ctx.scale(0.4,0.4);
        // ctx.rotate(-Math.PI/2);
        ctx.strokeStyle = "black";
        ctx.fillStyle = "white";
        ctx.lineWidth = 8;
        ctx.lineCap = "round";

        // 12個小時 每隔30弧度一個點
        ctx.save();
        for (var i=0;i<12;i++){
            ctx.beginPath();
            ctx.rotate(30* Math.PI/180);  //畫布旋轉，每次旋轉30個弧度
            ctx.moveTo(100,0);
            ctx.lineTo(120,0);
            ctx.stroke();
        }
        ctx.restore();

        //分針
        ctx.save();
        ctx.lineWidth = 5;
        for (i=0;i<60;i++){
            if (i%5!=0) {
                ctx.beginPath();
                ctx.moveTo(117,0);
                ctx.lineTo(120,0);
                ctx.stroke();
            }
            ctx.rotate(Math.PI/30);
        }
        ctx.restore();
        
        var sec = now.getSeconds();
        var min = now.getMinutes();
        var hr  = now.getHours();
        hr = hr>=12 ? hr-12 : hr;

        ctx.fillStyle = "black";

        // write Hours
        ctx.save();
        ctx.rotate( hr*(Math.PI/6) + (Math.PI/360)*min + (Math.PI/21600)*sec )
        ctx.lineWidth = 14;
        ctx.beginPath();
        ctx.moveTo(-20,0);
        ctx.lineTo(80,0);
        ctx.stroke();
        ctx.restore();

        // write Minutes
        ctx.save();
        ctx.rotate( (Math.PI/30)*min + (Math.PI/1800)*sec )
        ctx.lineWidth = 10;
        ctx.beginPath();
        ctx.moveTo(-28,0);
        ctx.lineTo(112,0);
        ctx.stroke();
        ctx.restore();
        
        // Write seconds
        ctx.save();
        ctx.rotate(sec * Math.PI/30);
        ctx.strokeStyle = "#D40000";
        ctx.fillStyle = "#D40000";
        ctx.lineWidth = 6;
        ctx.beginPath();
        ctx.moveTo(-30,0);
        ctx.lineTo(83,0);
        ctx.stroke();
        ctx.beginPath();
        ctx.arc(0,0,10,0,Math.PI*2,true);
        ctx.fill();
        ctx.beginPath();
        ctx.arc(95,0,10,0,Math.PI*2,true);
        ctx.stroke();
        ctx.fillStyle = "rgba(0,0,0,0)";
        ctx.arc(0,0,3,0,Math.PI*2,true);
        ctx.fill();
        ctx.restore();

        ctx.beginPath();
        ctx.lineWidth = 14;
        ctx.strokeStyle = '#325FA2';
        ctx.arc(0,0,142,0,Math.PI*2,true);
        ctx.stroke();

        ctx.restore();
        window.requestAnimationFrame(clock);
     }

    window.requestAnimationFrame(clock);
   }
   </script>
    </body>
</html>

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