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

You can use the qualities of the abstract equality operator to do this:

if (variable == null){
    // your code here.
}

Because null == undefined is true, the above code will catch both null and undefined.