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

In JavaScript, as per my knowledge, we can check an undefined, null or empty variable like below.

if (variable === undefined){
}

if (variable === null){
}

if (variable === ''){
}

Check all conditions:

if(variable === undefined || variable === null || variable === ''){
}