self executing function jquery vs javascript difference

Question

What are the difference among -

First :-

(function () {

    var Book = \'hello\';

}());

Second:-

Answer 1

All three examples are Immediately Invoked Function Expressions (IIFE).

The only difference is that in the third example jQuery is being passed in as a variable allowing you to use it within the IIFE using its dollar naming convention. e.g.

(function ($) {
  var Book = 'hello';
  $('#bookelement').html(Book);
})(jQuery);

Answer 2

All of these are example of self invoking function.

This will give you a clear view:-

var my_func = function(){
    var internal_var = "Hello";
    return internal_var;
};

var my_func2 = function(name){
    var internal_var = "Hello";
    return internal_var;
};

var long_var_name = "I can be some object or number or object or array";

var result1 = (my_func());
var result2 = (my_func)();
var result3 = (my_func2)(long_var_name);

console.log(result1, result2, result3);

Using this example you can compare it with the First, Second and Third method.

Answer 3

As the other answers pointed out they are all self executing anonymous function or immediate anonymous functions.

The third example is use to create aliases for variables outside the function. This is a good way to prevent name conflicts and creating code where it's possible to easily change a module used in the function. It's essentially a form of dependency injection.

(function (doc, win, $, myModule) {
    // Code
}(document, window, jQuery, window.MYAPP.myModule));

doc, win, $ and myModule are injected variables. With this pattern it's trivial to change any of the injected components. Like this

(function (doc, win, $, myModule) {
    // Code
}(document, window, jQuery, window.MYAPP.myModule2)); //Use myModule2 instead myModule

Answer 4

Immediately-invoked function expressions (IIFE) is one of the core JavaScript features. Its main aim is not to clutter the namespaces with disposable functions and variables.

if you use a variable or a function only once, you don't need to make it available for the rest of the code (therefore you make a private access, for example). In case of functions, you may just let them be anonymous, just like the following:

(function(){
  console.log("Hello symfony world!");
}());

Please check with this link

Furthermore here is a useful explanatory video in less than 7 minutes

Answer 5

These all are self executing functions. Now days also known as Immediately Invoked Function Expressions (IIFE).

First two are exactly same with slightly different syntax and third is passing a parameter as jQuery object.

Answer 6

In all cases you are doing an anonymous function. I think 1 is the same as 2. In the third case you are passing jQuery as an argument. This is done when you want to encapsulate jQuery within your function's scope.

For instance, in your application, jQuery var could be jQuery. But within your anonymous function you may want to use it as $.

(function ($) {
    //Here jQuery is $
    var Book = $(document.body).text();    

})(jQuery);

//Out of your function, you user jQuery as jQuery (in this example)
var Book = jQuery(document.body).text();