本文实例讲述了JavaScript+html5 canvas绘制时钟效果。分享给大家供大家参考，具体如下：
HTML部分：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0,minimum-scale=1.0,maximum-scale=1.0"> <title>canvas绘图</title> </head> <body onload="init()"> <canvas id="canvas" width="200px" height="200px"></canvas> </body> </html>
JavaScript部分：
function init(){ var canvas = document.getElementById("canvas"), context = canvas.getContext("2d"); setInterval(function(){draw(canvas, context)},1000); } function draw(canvas, context){ var x = canvas.width, y = canvas.height, r = Math.min(x/2, y/2); context.clearRect(0, 0, x, y); //清除绘画历史 //绘画钟框 context.fillStyle = "#f1f1f1"; drawCircle(context, x, y, r); //绘画文字 var tx = x/2,ty = y/2,tr = 0.8*r; context.font = "bold 12px 微软雅黑"; context.fillStyle = "#000"; drawText(context, "1", tx + 0.5*tr,ty - 0.866*tr); drawText(context, "2", tx + 0.866*tr, ty - 0.5*tr); drawText(context, "3", tx + tr, ty); drawText(context, "4", tx + 0.866*tr, ty + 0.5*tr); drawText(context, "5", tx + 0.5*tr, ty + 0.866*tr); drawText(context, "6", tx, ty + tr); drawText(context, "7", tx - 0.5*tr, ty + 0.866*tr); drawText(context, "8", tx - 0.866*tr, ty + 0.5*tr); drawText(context, "9", tx - tr, ty); drawText(context, "10", tx - 0.866*tr, ty - 0.5*tr); drawText(context, "11", tx - 0.5*tr, ty - 0.866*tr); drawText(context, "12", tx, ty - tr); //获取当前时间 var date = new Date(), h = date.getHours(), m = date.getMinutes(), s = date.getSeconds(), angleH = (360/12)*Math.PI/180, angleM = (360/60)*Math.PI/180 context.strokeSyle = "#000"; //绘制时刻度 drawScale(context, x, y, r, angleH, -0.88*r, -0.96*r, 3); //绘制分刻度 drawScale(context, x, y, r, angleM, -0.93*r, -0.96*r, 1); //绘画时分秒针 drawCircle(context, x, y, 3); drawNeedle(context, x, y, r, h*angleH + m*angleM/12, -0.5*r); drawNeedle(context, x, y, r, m*angleM + s*angleM/60, -0.6*r); drawNeedle(context, x, y, r, s*angleM, -0.75*r); } //绘画圆 function drawCircle(context, x, y, r){ context.save(); context.beginPath(); context.arc(x/2, y/2, r, 0, Math.PI*2, 0); context.fill(); context.closePath(); context.restore(); } //绘画文字方法 function drawText(context, text, x, y){ context.save(); x -= (context.measureText(text).width/2); y += 4; context.translate(x, y); context.fillText(text, 0, 0); context.restore(); } //绘制刻度方法 function drawScale(context, x, y, r, rotate, start, end, lineWidth){ context.save(); context.beginPath(); context.translate(x/2,y/2); context.lineWidth = lineWidth; for (var i = 0; i < 60; i++) { context.rotate(rotate); context.moveTo(0, start); context.lineTo(0, end); } context.closePath(); context.stroke(); context.restore(); } //绘画时分秒针方法 function drawNeedle(context, x, y, r, rotate, line){ context.save(); context.translate(x/2,y/2); context.beginPath(); context.rotate(rotate); context.moveTo(0, 0.1*r); context.lineTo(0, line); context.closePath(); context.stroke(); context.restore(); }
希望本文所述对大家JavaScript程序设计有所帮助。