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.