一段代码

请用JavaScript编写一个Car类，包含：一个属性pertrol，表示车辆目前剩余的汽油方法run，每调用一次，汽车的pertrol含量就会减一方法clone,用于深度复制Car对象方法cloneCount，用于获取clone的次数，使用clone方法复制得到的对象的cloneCount应被重置为0。请考虑Car类可能会被继承的情况下的最优方案

function Car(l){		
		this.pertrol= l || 200;		
		this.cloneNum = 0;				
	}
	Car.prototype = {
			constructor : Car,
			clone:function(){
				this.cloneNum++;
				function sub(){
					
				}
				sub.prototype = this.constructor.prototype;
				var clone = new sub();
				for(var i in this){
					if(this.hasOwnProperty(i)){
						clone[i]=this[i];
					}
				}
				clone.cloneNum=0;
				return clone;
			},
			cloneCount:function(){
				return this.cloneNum;
			},
			run:function(){
				
			}
				
	}
			
	var carA = new Car();	
	var c1 = carA.clone();  //c1 carA cloneNum=1,  c1  cloneNum=0;
	var c2 = carA.clone();  //c2 carA cloneNum=2,  c2  cloneNum=0;
	var cc1 = c1.clone();  //cc1 c1 cloneNum=1,  cc1  cloneNum=0;
	var cc1a = c1.clone();
	var cc1b = c1.clone();
	
	var $carA_cloneCount = carA.cloneCount();
	var $c1_cloneCount = c1.cloneCount();
	var $c2_cloneCount = c2.cloneCount();
	var $cc1_cloneCount = cc1.cloneCount();

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