// As a function
Evan.isUndefined = function(u) {
	return typeof u === 'undefined';
};

// In an "if"
if (typeof foo === 'undefined') {
	// ...
}

Checking for `undefined` in JavaScript is weird (the variable can be redefined), so I made a function to do it. This stuff (and others) is also in my [JSTypes](https://github.com/EvanHahn/JSTypes) type-checking library.

Is something undefined in JavaScript?

JavaScript