canvas基础绘制-绚丽倒计时的实例

var WINDOW_WIDTH = 1024;
var WINDOW_HEIGHT = 768;
var RADIUS = 8;
var MARGIN_TOP = 60;
var MARGIN_LEFT = 30;

var endTime = new Date();//const声明变量，不可修改，必须声明时赋值；
endTime.setTime( endTime.getTime() + 3600*1000);//当前时间向后一小时；
var curShowTimeSecOnds= 0;

var balls =[];
const colors = ["#33B5E5","#0099CC","#AA66CC","#9933CC","#99CC00","#669900","#FFBB33","#FF8800","#FF4444","#CC0000"];

window.Onload= function () {
 //屏幕自适应
 WINDOW_WIDTH = document.body.clientWidth;
 WINDOW_HEIGHT = document.body.clientHeight;

 RADIUS = Math.round(WINDOW_WIDTH*4/5/108)-1;

 MARGIN_TOP = Math.round(WINDOW_HEIGHT/5);
 MARGIN_LEFT = Math.round(WINDOW_WIDTH/10);

 var canvas = document.getElementById("canvas");
 var cOntext= canvas.getContext("2d");

 canvas.width = WINDOW_WIDTH;
 canvas.height = WINDOW_HEIGHT;

 curShowTimeSecOnds= getCurrentShowTimeSeconds();
 setInterval(
  function () {
   update();
   render(context);
 },50)

};

function getCurrentShowTimeSeconds() {
 var curTime = new Date();//获取目前时间；
 var ret = endTime.getTime()-curTime.getTime();
 ret = Math.round(ret/1000);//获取秒数差值；
 return ret>=0&＃63;ret:0;
}

function update() {

 var nextShowTimeSecOnds= getCurrentShowTimeSeconds();

 var nextHours = parseInt(nextShowTimeSeconds/3600);
 var nextMinutes = parseInt((nextShowTimeSeconds-nextHours*3600)/60);
 var nextSecOnds= nextShowTimeSeconds%60;

 var curHours = parseInt(curShowTimeSeconds/3600);
 var curMinutes = parseInt((curShowTimeSeconds-curHours*3600)/60);
 var curSecOnds= curShowTimeSeconds%60;

 if(nextSeconds!=curSeconds){
  if(parseInt(curHours/10)!=parseInt(nextHours/10)){
   addBalls(MARGIN_LEFT+0,MARGIN_TOP,parseInt(curHours/10));
  }
  if(parseInt(curHours%10)!=parseInt(nextHours%10)){
   addBalls(MARGIN_LEFT+15*(RADIUS+1),MARGIN_TOP,parseInt(curHours%10));
  }

  if(parseInt(curMinutes/10)!=parseInt(nextMinutes/10)){
   addBalls(MARGIN_LEFT+39*(RADIUS+1),MARGIN_TOP,parseInt(curMinutes/10));
  }
  if(parseInt(curMinutes%10)!=parseInt(nextMinutes%10)){
   addBalls(MARGIN_LEFT+54*(RADIUS+1),MARGIN_TOP,parseInt(curMinutes%10));
  }

  if(parseInt(curSeconds/10)!=parseInt(nextSeconds/10)){
   addBalls(MARGIN_LEFT+78*(RADIUS+1),MARGIN_TOP,parseInt(curSeconds/10));
  }
  if(parseInt(curSeconds%10)!=parseInt(nextSeconds%10)){
   addBalls(MARGIN_LEFT+93*(RADIUS+1),MARGIN_TOP,parseInt(curSeconds%10));
  }

  curShowTimeSecOnds= nextShowTimeSeconds;
 }
 
 updateBalls();
}
function updateBalls() {

 //循环遍历每一个彩色动画小球
 for(var i=0;i=WINDOW_HEIGHT){
   balls[i].y = WINDOW_HEIGHT-RADIUS;
   balls[i].vy = -balls[i].vy*0.75;
  }
 }

 // 如果小球出了画布，就清除小球,性能优化
 var cnt = 0;
 for(var i=0;i0&&balls[i].x+RADIUSMath.min(300,cnt)){
  balls.pop();
 }
}

function addBalls(x,y,num) {


 for (var i = 0; i