Declaring a JavaScript function that is inside a variable?

Question

I'm reading this tutorial: http://nathansjslessons.appspot.com/

Inside there's a lessons that says:

// A simple function that adds one
var plusOne = function (x) {
    return x + 1;
};

I'm used to see functions like this:

function myFunction() {
    return x + 1;
};

What's the difference between the first and the second?

Answer 1

The only difference is the first function:

var plusOne = function (x) {
    return x + 1;
};

is defined at runtime, whereas another function:

function myFunction() {
    return x + 1;
};

is defined at parse time for the script block.