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

I've just had this problem i.e. checking if an object is null.
I simply use this:

if (object) {
    // Your code
}

For example:

if (document.getElementById("enterJob")) {
    document.getElementById("enterJob").className += ' current';
}