Argument passing into IIFE

Question

Do anyone can explain and prove which one of examples is "more correct"?

A: pass object as an argument

(function($){
    $.doStuff();
})(jQuery);

B: retrieve object within the function

(function(){
    var $ = jQuery;
    $.doStuff();
})();

I really like B because of its readability. Only technical difference between A and B is that B has to lookup one more scope. I consider this as marginal difference so why is "recomended" the A way?

Note that the jQuery is just example. Important is the nature of the problem: Pass as argument or retrieve within the function?

Answer 1

Both are equivalent, but I like the first example (passing as an argument) more as it saves you one line of code. That also means that your function does not contain unnecessary logic.

Answer 2

The second way will only work if the name of the jQuery library is really "jQuery". It's possible (though unusual) to call .noConflict() like this:

window.banana = jQuery.noConflict( true );

Then, your first example would still work:

(function($) {
  $.doStuff();
})( banana );

but your second example would fail (as written). Of course, you could similarly hard-code the name "banana" into the second one too, but if that function isn't directly under your control, you can't; plus it's a "DRY" violation.

Imagine that you've got an initialization function being loaded in a separate JavaScript source file; perhaps it's a 3rd-party script. If you want to call that function at initialization time, you'll have more flexibility if the function takes the jQuery reference as a parameter instead of just making the assumption that the global symbol is anything in particular.

alienInitializationFunction( banana );

will still work, in other words.