Calling a function from an attempt to create a namespace and namespace is 'undefined'

I was looking at how to create a namespace in Jquery and create a kind of a class that one would create in C#, I read through this article and came up with this in a seperate JS file

var GlobalScript = {
    myStuff: function(){
        alert("hi");
    }
}

and I have tried calling the function like this in another external file..

$("#btnSave").click(function(){
    GlobalScript.myStuff();
});

and when it gets called I am getting an error in saying that it undefined, what am I doing wrong?