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

The shortest and easiest:

if(!EmpName ){
 // DO SOMETHING
}

this will evaluate true if EmpName is:

• null
• undefined
• NaN
• empty
• string ("")
• 0
• false