How do you access constructors variables?

Question

I have a "class" within Javascript with a variable assigned in the constructor. I also use prototype to store variables/methods:

var MyClass = function() 
{ 
    this.age = 100;
};

MyClass.prototype.name = "John";
MyClass.prototype.getAge = function() { return this.age};

alert(MyClass.prototype.name); //Alerts John
alert(MyClass.age); //undefined as expected
alert(MyClass.prototype.getAge()); //undefined??

So from what I can tell, there is no way I can access the constructor variables that are stored within MyClass unless I create an object from the Class:

var theClass = new MyClass();
alert(theClass.age);
alert(theClass.getAge());

Both alerts will return the age correctly.

So to reiterate, can I access the constructor variables directly from the MyClass without needing to create a variable?

Regarding alert(MyClass.prototype.getAge()); //undefined??: It would try to access MyClass.prototype.age which does not exist. Inside the constructor this refers to an empty object with inherits from MyClass.prototype, so age will never be assigned to MyClass.prototype. — Felix Kling
– Felix Kling, Commented May 24, 2012 at 13:04

Ernest Friedman-Hill · Accepted Answer · 2012-05-24 12:58:00Z

2

No. The variable age in your example is created when the constructor function runs; therefore it's not going to be available until you run the function.

answered May 24, 2012 at 12:58

Ernest Friedman-Hill

81.9k11 gold badges158 silver badges192 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Quentin · Accepted Answer · 2012-05-24 12:58:09Z

2

So from what I can tell, there is no way I can access the constructor variables that are stored within MyClass unless I create an object from the Class

Correct. They are assigned in the function body. They won't exist until the function is executed.

So to reiterate, can I access the constructor variables directly from the MyClass without needing to create a variable?

No.

answered May 24, 2012 at 12:58

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

Collectives™ on Stack Overflow

How do you access constructors variables?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related