canvas画时钟

<!DOCTYPE html>

<html>

    <head>

        <meta charset="utf-8">

        <meta http-equiv="X-UA-Compatible" content="IE=edge">

        <title>canvas画时钟</title>

        <script>

        window.onload = function() {

            var canvas = document.getElementById("canvas");

            canvas.width = canvas.height = 400;

            canvas.style.background = "white";

            if (canvas.getContext) {

                var ext = canvas.getContext("2d");

                drawClock()

                setInterval(drawClock, 1000);

            }

            function drawClock() {

                var x = 200;

                var y = 200;

                var r = 150;

                ext.clearRect(0, 0, canvas.width, canvas.height)

                var oData = new Date();

                var hours = oData.getHours();

                var minutes = oData.getMinutes();

                var seconds = oData.getSeconds();

                var hoursValue = (-90 + hours * 30 + minutes / 2) * Math.PI / 180; //分针过了30，时针不应该正好在整点上，2分钟一度；

                var minutesValue = (-90 + minutes * 6) * Math.PI / 180;

                var secondsValue = (-90 + seconds * 6) * Math.PI / 180;

                ext.lineWidth = 2

                ext.arc(x, y, r, 0, Math.PI * 2, false);

                ext.stroke();

                //画小刻度

                for (var i = 0; i < 60; i++) {

                    ext.strokeStyle = "black"

                    ext.lineWidth = 1;

                    ext.beginPath();

                    ext.moveTo(x, y);

                    ext.arc(x, y, r, 6 * i * Math.PI / 180, 6 * (i + 1) * Math.PI / 180, false)

                    ext.closePath();

                    ext.stroke();

                }

                drawBlankCircle(10)

                    //画大刻度

                for (var i = 0; i < 12; i++) {

                    ext.lineWidth = 3;

                    ext.strokeStyle = "green"

                    ext.beginPath();

                    ext.moveTo(x, y);

                    ext.arc(x, y, r, 30 * i * Math.PI / 180, 30 * (i + 1) * Math.PI / 180, false)

                    ext.closePath();

                    ext.stroke();

                }

                drawBlankCircle(15)

                    //画空白覆盖圆;

                function drawBlankCircle(d) {

                    ext.fillStyle = "white"

                    ext.beginPath();

                    ext.arc(x, y, r - d, 0, Math.PI * 2, false);

                    ext.closePath();

                    ext.fill();

                }

                //画时针;

                ext.lineWidth = 5;

                ext.strokeStyle = "#f90"

                ext.beginPath();

                ext.moveTo(x, y);

                ext.arc(x, y, r - 60, hoursValue, hoursValue, false);

                ext.closePath();

                ext.stroke();

                //画分针;

                ext.lineWidth = 3;

                ext.strokeStyle = "red"

                ext.beginPath();

                ext.moveTo(x, y);

                ext.arc(x, y, r - 40, minutesValue, minutesValue, false);

                ext.closePath();

                ext.stroke();

                //画秒针;

                ext.lineWidth = 1;

                ext.strokeStyle = "black"

                ext.beginPath();

                ext.moveTo(x, y);

                ext.arc(x, y, r - 25, secondsValue, secondsValue, false);

                ext.closePath();

                ext.stroke();

                //画表盘中心小圆;

                ext.fillStyle = "black";

                ext.beginPath();

                ext.arc(x, y, 6, 0, Math.PI * 2, false);

                ext.closePath();

                ext.fill();

            }

        }

        </script>

    </head>

    <body >

        <canvas id="canvas">

        </canvas>

    </body>

</html>
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