Dollar sign before self declaring anonymous function in JavaScript?

Question

What is the difference between these two:

$(function () {
    // do stuff
});

AND

(function () {
    // do stuff
})();
         


        

Answer 1

They are both anonymous functions, but (function(){})() is called immediately, and $(function(){}) is called when the document is ready.

jQuery works something like this.

window.jQuery = window.$ = function(arg) {
    if (typeof arg == 'function') {
        // call arg() when document is ready
    } else {
       // do other magics
    }
}

So you're just calling the jQuery function and passing in a function, which will be called on document ready.

The 'Self-executing anonymous function' is the same as doing this.

function a(){
    // do stuff
}
a();

The only difference is that you are not polluting the global namespace.