代码没报错就是逻辑问题 可能是你的draw（）没放到主函数main里 也可能是你的出生代码无效

我的 你对比下吧

希望能对你有帮助

var fruitObj=function()

{

this.alive=[];//bool

this.y=[];

this.x=[];

this.l=[];

this.spd=[];

this.fruitType=[];

this.orange=new Image();

this.blue=new Image();

}

fruitObj.prototype.num=30;

fruitObj.prototype.init=function()

{

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

{

this.alive[i]=false;

this.x[i]=0;

this.y[i]=0;

this.spd[i]=Math.random()*0.017+0.003;//[0.005,0.015)

        this.fruitType[i]="";

}

this.orange.src="./src/fruit.png";

this.blue.src="./src/blue.png";

}

fruitObj.prototype.draw=function()

{

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

{

if(this.alive[i])//为什么不是this。alive[i]=true

{

if(this.fruitType[i]=="blue")

{

var pic=this.blue;

}

else{

var pic =this.orange;

   }

if(this.l[i]<15)

{

this.l[i]+=this.spd[i]*daltaTime;

}

else

{

this.y[i]-=this.spd[i]*7*daltaTime;

}

ctx2.drawImage(pic,this.x[i]-this.l[i]*0.5,this.y[i]-this.l[i]*0.5,this.l[i],this.l[i]);

if(this.y[i]<(Math.random()*50+20))

{

this.alive[i]=false;

}

}

     }

}

fruitObj.prototype.born=function(i)

{

var aneID=Math.floor(Math.random()*ane.num);

this.x[i]=ane.x[aneID];

this.y[i]=canHeight-ane.len[aneID];

this.l[i]=0;

this.alive[i]=true;

var run=Math.random();

if(run<=0.3)

{ 

this.fruitType[i]="blue";

    }

    else{

    this.fruitType[i]="orange";

        }

}

fruitObj.prototype.dead=function(i)

{

this.alive[i] = false;

}

function fruitMonitor()

{

var num=0;

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

{

if(fruit.alive[i]) num++;

}

if (num<15) 

{

sendFruit();

return;

    }

}

function sendFruit()

{

    for(var i=0; i<fruit.num; i++)

    {

                      if (!fruit.alive[i]) 

           {

        fruit.born(i);

        return;

           }

    }   

}