Question

Can I write nested classes in Javascript?

function A()
{
    this.a;
    this.B = function()
    {
      this.ab ;
      this.C  = function()
      {
         this.ab = 0;
      }
    }
}

If the above code is correct,then

1.How do I declare an object of type B
2.Whose property is  ab.A() 's  or B() 's?.
3.Inside B() where does the 'this' points to.To A() Or to B()?

Answer 1

Abstract:

Calling to function without using new operator means that this will be refer to object in which that function was created.
For global variables this object is window object.
Calling using new – function behave as constructor like in classes and this refers to this instance which will been created

1.How do I declare an object of type B

First way( as a curiosity ) – by calling to A without using new operator this will be refer to windowobject and B method and all other what was declared with this leaks to global scope because A == window.A => true

A(); 
var b = new B; // means => new window.B  //parentheses can be ommited if you invoking without arguments  
alert( ab )  // alerts 'inside A'  -> value from code presented below

or from instance of A:

new new A().B  // means => new ( new A ).B  

Be careful.

2.Whose property is ab.A() ‘s or B() ‘s?.

As above, it depends of how we’ll accessing to it:

 function A()
    {
        this.ab = "inside A";
        this.B = function()
        {
          this.ab = "inside B";
          this.c  = function()
          {  
             this.ab = "inside C";
          }
        }
    };

Check this out

var a = new A;
a.ab // "inside A"
a.B(); // in B now 'this' refers to 'a', 'a.ab' will be replaced to 'ab' from inside 'B'
a.ab // "inside B"

but

var a = new A;
a.ab // "inside A"
var b = new a.B;
a.ab // "inside A"
b.ab // "inside B"

// and now
b.c() 
b.ab // "inside C" and so on:)  

3.Inside B() where does the ‘this’ points to.To A() Or to B()?

As above:)