<Meta charset="UTF-8"> <Meta name="Generator" content="EditPlus®"> <Meta name="Author" content=""> <Meta name="Keywords" content=""> <Meta name="Description" content="">

var canvas=document.getElementById("canvas"); var context=canvas.getContext("2d"); canvas.width=window.innerWidth; canvas.height=window.innerHeight; function Circle(){ this.x=Math.random()*canvas.width; this.y=canvas.height; this.r=Math.random()*10; //绘制圆形 this.paint=function(){ context.beginPath(); context.arc(this.x,this.y,this.r,Math.PI*2); context.fillStyle="white"; context.globalAlpha = 0.5; context.fill(); } //控制圆形移动 this.step=function(){ this.y--; } } var circles=[]; function createCircles(){ var circle=new Circle();//?????? circles[circles.length]=circle; }

function paintCircles(){
for(var i=0;i<circles.length;i++){
circles[i].paint();
}
}
function stepCircles(){
for(var i=0;i<circles.length;i++){
circles[i].step();
}
}
var myimg=new Image();
myimg.src="images/demo-1.png";
var timer="";
setInterval(function(){
context.drawImage(myimg,0);
timer++;
if(timer%20==0){
createCircles();
}
paintCircles();
stepCircles();
},10);