javascript中的构造函数问题

如果我写两个构造函数，如下所示：

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

及

有什么区别？做

赛名

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第一段代码中真的有什么意思吗？它有用吗？

sayName

在第一个代码中是一个私有全局函数，而在第二个代码中是一个特权公共函数

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更新#1：

下面的代码大致概括了它们的含义

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

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实际上，因为没有

var

关键字，所以它是一个全局变量function@qwertymk呜呜声。错过了要点。@jsnewman更新了答案，为之前的错误答案道歉。当你询问有关书籍的问题时，请包括有关该作品的信息。它可以帮助人们帮助您，以及正确地对代码进行归因。在本例中，示例来自Nicholas C.Zakas的《面向Web开发人员的专业JavaScript》，第二版（Wrox，2009），第152页。

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