Constructor question in javascript

Question

If I write two constructors like these below:

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

and

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

What is the difference? Does

sayName

really mean something in the first code? Is it useful?

• Dori: When you're asking questions about books, please include information about the work. It helps people help you, as well as correctly attributing the code. In this case, the example is from Professional JavaScript for Web Developers, Second Edition by Nicholas C. Zakas (Wrox, 2009), page 152.

Answer 1

sayName in the first code is a (削除) private (削除ここまで) global function, while in second it's a privileged public function.

---

Update#1:

The following code pretty much summarizes what they mean

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

• qwertymk: actually since there's no var keyword it's a global function
• Nishant: @qwertymk woops. missed the fine-line.
• Nishant: @jsnewman updated answer, apology for the messed up answer earlier.