js函数闭包内存泄露问题

原始代码：

function Cars(){
  this.name = "BMW";
  this.color = ["white","black"];
}
Cars.prototype.sayColor = function(){
  var outer = this;
  return function(){
    return outer.color
  };
};
 
var instance = new Cars();
console.log(instance.sayColor()())

优化代码： 

function Cars(){
  this.name = "BMW";
  this.color = ["white","black"];
}
Cars.prototype.sayColor = function(){
  var outerColor = this.color; //保存一个副本到变量中
  return function(){
    return outerColor; //应用这个副本
  };
  outColor = null; //释放内存
};
 
var instance = new Cars();
console.log(instance.sayColor()())