果实没出现

var fruitObj=function()
{
	this.alive=[];//bool
	this.x=[];
	this.y=[];
	this.orange=new Image();
	this.blue=new Image();
}
fruitObj.prototype.num=30;

fruitObj.prototype.init=function()
{
	console.log("init");
	for(var i=0;i<this.num;i++)
	{
		this.alive[i]=true;
		this.x[i]=0;
		this.y[i]=0;
		this.born(i);
	}
	this.orange.src="./src/fruit.jpg";
	this.blue.src="./src/blue.jpg"
}
fruitObj.prototype.draw=function()
{
	console.log("draw");
	for(var i=0;i<this.num;i++)
	{
		//draw,find an ane,grow,fly up
		ctx2.drawImage(this.orange,this.x[i]-this.orange.width*0.5,this.y[i]-this.orange.height*0.5);//果实没出现，提示这里有问题
	}
	
}
fruitObj.prototype.update=function()
{
	var num=0;
	for(var i=0;i<this.num;i++)
		if(this.alive[i]) num++;
}
fruitObj.prototype.born=function(i)
{
	console.log("born");
	var aneID=Math.floor(Math.random()*ane.num);
	this.x[i]=ane.x[aneID];
	this.y[i]=canHeight-ane.len[aneID];
}
请问是什么原因呀