var property vs this.property in object constructor in javascript?

Question

Is there any difference between "this.property" vs "var property" inside object constructor?

example:

var person = function(){
    var age;
    this.firstName;        
}

Answer 1

Yes. For example, if you instantiate a new person like so:

var p = new person();

You will be able to access the firstName variable from outside, which becomes a property of the new object:

console.log(p.firstName); // whatever you assigned it to

But not the age variable, whose scope is limited to inside the function body:

console.log(p.age); // undefined

Answer 2

this.property returns the property of the calling object. In this case, the one calling person() function.

var property just define a variable whose scope is the function person()