Why does “undefined equals false” return false?

Question

When I compare undefined and null against Boolean false, the statement returns false:

undefined == false;
null == false;

It return false. W

Answer 1

Undefined is not the same thing as false, false is a boolean object (which has a value of 0 therefore it is indeed defined).

An example:

var my_var;
var defined = (my_var === undefined)
alert(defined);  //prints true.  It is true that my_var is undefined

my_var = 22;
defined = (my_var === undefined)
alert(defined);  //prints false.  my_var is now defined

defined = (false === undefined)
alert(defined);  //prints false, false is defined

defined = (true === undefined)
alert(defined);  //prints false, true is defined