waveObj.prototype.draw=function(){

ctx1.save();

ctx1.linWidth=2;

ctx1.shadowBlur=10;

ctx1.shadowColor="white";

for(var i=0;i<this.num;i++){

if(this.alive[i]){

this.r[i]+=deltatime+0.05;//半径逐渐变大

if(this.r[i]>60){

this.alive[i]=false;

break;

} 

var alpha=1-this.r[i]/60;//r与alpha成反比

//draw  canvas arc()绘制圆的方法

ctx1.beginPath();

ctx1.arc(this.x[i],this.y[i],this.r[i],0,Math.PI*2);

ctx1.strokeStyle="rgba(255,255,255,"+alpha+")";

ctx1.stroke();

ctx1.closePath();

}

}

ctx1.restore();

}