fruit 里面的 num为什么可以直接引用？

Question

按照道理不是应该是fruit里面的fruitObj的num吗

按照老师的代码对照了好几遍，还是不行。名字也没打错

以下是代码

var fruitObj =function(){

      this.alive =[];
      this.x=[];
      this.y=[];
      this.l=[];
      this.spd=[];
      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()*0.01+0.005;     
            
       }

        this.orange.src="./src/fruit.png";
        this.blue.src="./src/blue.png";
        
}
fruitObj.prototype.draw= function(){
       
         for( var i=0;i< this.num;i++){
              
                 //draw
                 //find an ane,grow,fly up
             if ( this.alive[i]){
		               if(this.l[i]<=14){
		               	  this.l[i]+=this.spd[i] *deltaTime;
		               }
		               else{

		                       this.y[i]-= this.spd[i]*5 *deltaTime;

		               }
		                 ctx2.drawImage(this.orange,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]<0-this.orange.width){

		                   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;

}

function fruitMonitor(){
      var num=0;
	    for(var i= 0;i<fruit.num;i++)
        {
        	 if( fruit.alive[i]  ) num++
        }
   
      if(num<15){
             sendFruit();
      	     return;
      }

        console.log("ni");
}

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

                 if (!fruit.alive[i]) {

                 	 fruit.born(i);
                 	 return;
                 }

           }
   

}

Answer 1

fruit是fruitObj实例出来的对象吧，所以可以直接调用fruitObj类的属性num.