Why is null an object and what's the difference between null and undefined?

Question

Why is null considered an object in JavaScript?

Is checking

if ( object == null )
      Do something

the

Answer 1

Look at this:

   
                                          //return:
nothing    //undefined    null    false
null   //object       null    false
empty    //string               false
zero      //number               false
int       //number               true
str     //string               true