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

typeof null;      // object
typeof undefined; // undefined

The value null represents the intentional absence of any object value. It is one of JavaScript's primitive values and is treated as falsy for boolean operations.

var x = null;
var y;

x is declared & defined as null

y is declared but not defined. It is declared with no value so it is undefined.

z is not declared so would also be undefined if you attempted to use z.