Chapter 4, Objects

Lets solve the following exercises:

Exercises

1. What happens here? What is this and what's o?

           function F() { 
             function C() { 
               return this; 
             } 
             return C(); 
           } 
           var o = new F(); 
   

   Here, this === window because C() was called without new.

   Also o === window because new F() returns the object returned by C(), which is this, and this is window.

   You can make the call to C() a constructor call:

           function F() { 
             function C() { 
               return this; 
             } 
             return new C(); 
           } 
           var o = new F(); 
   

   Here, this is the object created by the C() constructor. So is o:

           > o.constructor.name; 
           "C" 
   

   It becomes more interesting with ES5's strict mode. In the strict mode, non-constructor invocations result in this being undefined, not the global object. With "use strict" inside F() or C() constructor's body, this would be undefined...