Inheriting parent's properties in a Javascript child object

Question

If I have these 2 functions:

function Person(age)
{
   this.setAge = function(newAge)
   {
       age = newAge;
   }

   this.getAge = function()
   {
      alert(age);
   }
}

function Bob(age)
{
    Person.call(this, age);
    this.foo = function() {} //etc
}

Bob.prototype = new Person();

bob = new Bob(43);
bob.getAge();

Will the correct age (43) be alerted?

Answer 1

The answer is yes but calling setAge will not change the foo functions version of age since they are different captured variables. Consider moving to a style that looks more like,

function Person(age) { this.age = age; }
Person.prototype.getAge = function() { return this.age; };
Person.prototype.setAge = function(value) { this.age = value; }
function Bob(age) { Person.call(this, age); }
Bob.prototype = new Person();
Bob.prototype.foo = function() { /* ... */ }

Note that foo() and getAge() now see the same value for this.age . Also this is much more space efficient since the instance of Person and Bob only consume one slot per instance instead of 3 to 4 and do not require closure environments to be created for getAge, setAge and foo.