立即调用函数表达式和文档就绪函数

Question

In Javascript using jQuery i can add scope to the function using Immediately Invoked Function Expression and pass the function jQuery, and name the parameter $

(function ( $ ) { 

    $.fn.greenify = function() {
        this.css( "color", "green" );
        return this;
    }; 

}( jQuery ));

Similarly, we write document ready function as below

$(function() {
    console.log( "ready!" );
    // use $ variable here
});

Does that mean document ready function is already scoped?
Do i also need to pass the function jQuery, and name the parameter $ in document ready function? something like below

$(function ( $ ) {
    console.log( "ready!" ); 
    // use $ variable here   
 }( jQuery ));

Answer 1

The IIFE is invoked immediately, it won't wait for document to get ready. So:

(function($) {

    // here document is not necessarly ready

})(jQuery);

When you do $(function() { ... }); you are not creating an IIFE, you are just passing a function (callback) to be executed when the document is ready.

If you want to do both, then use:

(function($) {

    $(function() {

        // here, document is really ready
        // $ available here too

    });

})(jQuery);

Or do it like this (using the fact that jQuery passes itself as parameter to its ready callback ):

jQuery(function($) {

    // here, document is really ready
    // and $ is obviously available (only here)

});