js时钟效果

【实例简介】

使用H5的canvas配合js实现的时钟效果
【实例截图】

【核心代码】

var c = document.getElementById("clock");
var ctx = c.getContext("2d");
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r =width / 2;
var rem = width / 200;
function drawBackground(){
 ctx.save();
 ctx.translate(r,r);
 ctx.beginPath();
 ctx.lineWidth = 7 * rem;
 ctx.arc(0,0,r - ctx.lineWidth / 2,0,2*Math.PI,false);
 ctx.stroke();
 var hourNumbers = [3,4,5,6,7,8,9,10,11,12,1,2];
 ctx.font = 18 * rem 'px Arial';
 ctx.textAlign = 'center';
 ctx.textBaseline = 'middle';
 hourNumbers.forEach(function(number,i){
  var rad = 2*Math.PI / 12 * i;
  var x = Math.cos(rad)*(r-30 * rem);
  var y = Math.sin(rad)*(r-30 * rem);
  ctx.fillText(number,x,y);
 });
 for(var i=0;i<60;i ){
  var rad =2 * Math.PI /60 * i;
  var x = Math.cos(rad)*(r-18 * rem);
  var y = Math.sin(rad)*(r-18 * rem);
  ctx.beginPath();
  if(i%5 ===0){
   ctx.fillStyle = '#000';
   ctx.arc(x,y,2 * rem,0,2*Math.PI,false);
  }else{
   ctx.fillStyle = '#ccc';
   ctx.arc(x,y,2 * rem,0,2*Math.PI,false);
  }
  
  ctx.fill();
 }

}
function drawHour(hour,minute){
 ctx.save();
 ctx.beginPath();
 var rad = 2 * Math.PI / 12 * hour;
 var mrad = 2 * Math.PI / 12 / 60 * minute;
 ctx.rotate(rad mrad);
 ctx.lineWidth = 5 * rem;
 ctx.lineCap = 'round';
 ctx.moveTo(0,10 * rem);
 ctx.lineTo(0, -r / 2);
 ctx.stroke();
 ctx.restore();
}
function drawMinute(minute){
 ctx.save();
 ctx.beginPath();
 var rad = 2 * Math.PI / 60 * minute;
 ctx.rotate(rad);
 ctx.lineWidth = 3 * rem;
 ctx.lineCap = 'round';
 ctx.moveTo(0,10 * rem);
 ctx.lineTo(0, -r 40 * rem);
 ctx.stroke();
 ctx.restore();
}
function drawSecond(second){
 ctx.save();
 ctx.beginPath();
 ctx.fillStyle='red';
 var rad = 2 * Math.PI / 60 * second;
 ctx.rotate(rad);
 ctx.moveTo(-2 * rem,20 * rem);
 ctx.lineTo(2 * rem,20 * rem);
 ctx.lineTo(1,-r 18 * rem);
 ctx.lineTo(-1,-r 18 * rem);
 ctx.fill();
 ctx.restore();
}
function drawDot(){
 ctx.beginPath();
 ctx.fillStyle = '#fff';
 ctx.arc(0,0,3 * rem,0,2*Math.PI,false);
 ctx.fill();
}

function draw(){
 ctx.clearRect(0,0,width,height);
 var now = new Date();
 var hour = now.getHours();
 var minute = now.getMinutes();
 var second = now.getSeconds();
 drawBackground();
 drawHour(hour, minute);
 drawMinute(minute);
 drawSecond(second);
 drawDot();
 ctx.restore();
}