Variable declaration

Hi there! That's actually a bit of a more advanced question than you think it is. And what I think you actually mean is this:

var count;  // this a variable with no data type... yet
var count = "";  // this is an empty string
var count = " " // this is a string containing a space

I'm going to put up some sample code and I want you to see what happens in the console. I think you'll be surprised by the first example.

var x;  // this variable is of type undefined... right now
console.log(x + 2);
console.log(x + "hello");

var y = "";  // this variable contains an empty string
console.log(y + 2);
console.log(y + "hello");

var z = 4;  // this variable holds a number
console.log(z + 2);
console.log(z + "hello");

Essentially, when you say var count; you are defining a variable that will later contain some sort of data. In many languages, you must explicitly specify what kind of data it will be holding. JavaScript is a little special and has something it calls "type inferencing" which means it makes a guess about what kind of data a variable will hold depending on how you're using it. But when it's never given an initial value, it can't make that guess. That's all fine and dandy until you try to use the + or some other mathematical function on it. It can combine a string and an integer. It can combine 2 integers. It can combine 2 strings. What it can't really do is combine something that is undefined and any one of those because it doesn't know what the result is supposed to be at the end.

So if you are guaranteed to give the variable an initial value later before you start manipulating the value with concatenation or mathematical operators then you don't need to give it an initial value. That being said, I generally give values that I know for a fact should hold a string later in my code an initial empty string value so that I don't run into just this scenario down the line.

Hope this clarifies things!