构造问题在javascript

Question

如果我写了两个构造这样的下面：

Person(name, age) { 
    this.name = name; 
    this.age = age; 
    sayName = function() { 
     alert("hello"); 
    }; 
} 

和

Person(name, age) { 
    this.name = name; 
    this.age = age; 
    this.sayName = function() { 
     alert("hello"); 
    }; 
} 

的区别是什么？是否

sayName

真的是第一个代码的东西吗？它有用吗？

Answer 1

sayName第一个代码是 私有 全局函数，而在第二个它是一个特权公共函数。

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更新＃1：

下面的代码几乎概括了他们的意思

function Person(name, age) { 
    this.name = name; 
    this.age = age; 
    sayName = function() { //define in global name-space 
    alert("hello"); 
    } 

    var sayNamePvt = function() { //private function 
     alert("hello pvt"); 
    } 

    this.callPvt = function(){ //shows how privilege function can access private vars and functions 
     sayNamePvt(); 
    } 
} 


function Person1(name, age) { 
    this.name = name; 
    this.age = age; 
    this.sayName = function() { //privilege public function 
     alert("hello1"); 
    } 
} 


var one = new Person('abc', 12); 
var two = new Person1('abcd', 11); 
two.sayName();//privileged public access 
sayName(); //global access 
//one.sayName(); //ERROR: one.sayName is not a function 
//one.sayNamePvt(); //ERROR: one.sayNamePvt is not a function 
one.callPvt(); //privileged method can call private functions