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I understand that you are just experimenting with closures, because your code should be a simple geter like that...

var object = {
 name : 'foo',
 getName : function(){ //closure
 return {
 a : 111,
 b : this.name, // variable th is avaliable in the inner scope
 c : function(){
 return this.b;
 }
 }
 }
};
object.getName().b // 'foo'

This does the same as your example:

var object = {
 name : 'foo',
 getName : (function(){ //closure
 var th=this; // a new var introduced in a closure
   return function(){ 
 return {
 a : 111,
 b : th.name, // variable th is avaliable in the inner scope
 c : function(){
 return this.b;
 }
 }
 }();
 })
};
object.getName().b // 'foo'

I understand that you are just experimenting with closures, because your code should be a simple geter like that...

var object = {
 name : 'foo',
 getName : function(){ //closure
 return {
 a : 111,
 b : this.name, // variable th is avaliable in the inner scope
 c : function(){
 return this.b;
 }
 }
 }
};
object.getName().b // 'foo'

This does the same as your example:

var object = {
 name : 'foo',
 getName : (function(){ //closure
 var th=this; // a new var introduced in a closure
   return function(){ 
 return {
 a : 111,
 b : th.name, // variable th is avaliable in the inner scope
 c : function(){
 return this.b;
 }
 }
 }();
 })
};
object.getName().b // 'foo'

[edit]

this in JS depends on where the function is called as well, so if you want a nice encapsulation Try this:

var object = {}
(function(){
 var _name='foo';
 object.getName=function(){
 return _name;
 }
});