网页计算器

效果

image-20210923193231968

代码

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<!DOCTYPE html>
<html>
    <head>
    <meta charset="utf-8" />
    <title>时钟</title>
    </head>
<canvas id="canvas"></canvas>

    <script>
        var canvas = document.getElementById("canvas");
        var ctx = canvas.getContext("2d");
        var radius = canvas.height / 2;
        
        Init();

        function Init()
        {
            window.addEventListener('resize', ResizeCanvas, false);
            ResizeCanvas();
        }

        function ResizeCanvas()
        {
            var s = Math.min(window.innerWidth, window.innerHeight);
            canvas.width = canvas.height = s;
            radius = canvas.height / 2;
            ctx.translate(radius, radius);

            radius *= 0.8;
            DrawClock();
        }

        setInterval(DrawClock, 1000);

        function DrawClock()
        {
            DrawFace(ctx, radius);
            DrawNumbers(ctx, radius);
            DrawTime(ctx, radius);
            DrawString(ctx, radius);
        }

        function DrawFace(ctx, radius)
        {
            var grad;
            ctx.beginPath();
            ctx.arc(0, 0, radius, 0, 2 * Math.PI);
            ctx.fillStyle = 'white';
            ctx.fill();

            grad = ctx.createRadialGradient(0, 0, radius * 0.9, 0, 0, radius);
            grad.addColorStop(0, '#333');
            grad.addColorStop(0.5, 'white');
            grad.addColorStop(1, '#333');
            
            ctx.strokeStyle = grad;
            ctx.lineWidth = radius * 0.1;
            ctx.stroke();

            ctx.beginPath();
            ctx.arc(0, 0, radius * 0.1, 0, 2 * Math.PI);
            ctx.fillStyle = '#333';
            ctx.fill();
        }

        function DrawNumbers(ctx, radius)
        {
            ctx.font = radius * 0.2 + "px arial";
            ctx.textBaseline = "middle";
            ctx.textAlign = "center";
            for (var num = 1; num <= 12; num++)
            {
                var ang = num * Math.PI / 6;
                ctx.rotate(ang);
                ctx.translate(0, -radius * 0.8);
                ctx.rotate(-ang);
                ctx.fillText(num.toString(), 0, 0);
                ctx.rotate(ang);
                ctx.translate(0, radius * 0.8);
                ctx.rotate(-ang);
            }
        }

        function DrawHand(ctx, pos, length, width)
        {
            ctx.beginPath();
            ctx.lineWidth = width;
            ctx.lineCap = "round";
            ctx.moveTo(0, 0);
            ctx.rotate(pos);
            ctx.lineTo(0, -length);
            ctx.stroke();
            ctx.rotate(-pos);
        }


        function DrawTime(ctx, radius)
        {
            var date = new Date();
            var hour = date.getHours();
            var minute = date.getMinutes();
            var second = date.getSeconds();

            hour = hour % 12;
            hour = (hour * Math.PI / 6) + (minute * Math.PI / (6 * 60)) + (second * Math.PI / (360 * 60));
            DrawHand(ctx, hour, radius * 0.5, radius * 0.05);
            minute = (minute * Math.PI / 30) + (second * Math.PI / (30 * 60));
            DrawHand(ctx, minute, radius * 0.8, radius * 0.03);
            second = (second * Math.PI / 30);
            DrawHand(ctx, second, radius * 0.9, radius * 0.02);
        }

        function DrawString(ctx, radius)
        {
            ctx.translate(0, -radius * 0.25);
            ctx.font = radius * 0.1 + "px arial";
            ctx.textBaseline = "middle";
            ctx.textAlign = "center";

            var date = new Date();

            var s = date.getFullYear().toString() + "-"
                + (date.getMonth() + 1).toString() + "-"
                + date.getDate().toString() + "  "
                + "星期 " + date.getDay().toString() + "  "
                + date.getHours().toString() + ":"
                + date.getMinutes().toString() + ":"
                + date.getSeconds().toString();
            ctx.fillText(s, 0, 0);

            ctx.translate(0, radius * 0.25);
        }

    </script>

</html>