JavaScript global variables & self-invoking anonymous functions

Question

So I've been reading through Javascript - The Good Parts and one thing that Crockford points out is the use weakness of global variables in Javascript, in such a way that if your product is expanded in some manner, and it relies on a 'global' variable it could be inadvertently set.

That's all good and fine and I understand the pros/cons of protecting variables, in other manners such as closures as well. However, I was doing some thinking, and wrapping code in a function like so:

(function () {
    var x = 'meh';
})();
(function () {
    alert(typeof x); // undefined
})();

gives it variable scope, which thereby prevents cross contamination of variables. I'm not sure if there's a blatant downside to this approach though and wondered if the community had any input, or if I'm just overthinking things and ignoring the main point.

Answer 1

That's a perfectly legal way of doing things -- the variables inside of your function (as long as they are prefaced by var) are local to the function. It's called the module pattern, and it's very well accepted.

Answer 2

To create applications with javascript, you must attempt to keep variables in a local scope, and anything inside a namespace. It's a good pratice and prevent a serie of harm codes and unespected behaviors.

read this

it's a article talking about the vantages of doing that.

Answer 3

Making it a global function is not the answer. Why wouldn't you do this? This keeps x out of the global namespace.

(function () {
    var x = 'meh';
    alert(typeof x);  //string
})();