How can I determine if a variable is 'undefined' or 'null'?

Question

How do I determine if variable is undefined or null?

My code is as follows:

var EmpN         


        

Answer 1

if (typeof EmpName != 'undefined' && EmpName) {

will evaluate to true if value is not:

• null

• undefined

• NaN

• empty string ("")

• 0

• false