When do I initialize variables in JavaScript with null or not at all?

Question

I have seen different code examples with variables declared and set to undefined and null. Such as:

var a; // undefined - unintentional value, object of type         


        

Answer 1

null is an object.. When something is undefined it is nothing.. it is not an object, neither a string, because it hasn't been defined yet.. obviously.. then it is simply a property with no function..

example:

You declare a variable with var but never set it.

var foo; 
alert(foo); //undefined.

You attempt to access a property on an object you've never set.

var foo = {};
alert(foo.bar); //undefined

You attempt to access an argument that was never provided.

function myFunction (foo) {
  alert(foo); //undefined.
}