Question

Are these both the same thing, i.e. ways of saying document ready:

$(function() {
  //
});

and

$(function($) {
   //
})(jQuery);

or is there a difference between the two, if so then when should I use which?

Answer 1

The first one is a shortcut for .ready().

The second one is simply invalid as you’re trying to call a non-callable object.

You probably meant this:

// v--------no $ at the beginning
    (function( $ ) {

       // simply a new lexical environment with a 
       //        local $ parameter pointing to jQuery

    })(jQuery);

…though it has nothing to do with DOM ready.

There is a variation on your first example that combines the two:

jQuery(function( $ ) {

  // DOM ready, and creates a local $ parameter pointing to jQuery

});