CODEWITHSUNDEEP
javascript
user3733648
user3733648

Reputation: 1333

What is the difference between two function signatures?

I would like to ask that what the main difference between 

(function(){
 ....
 ....
})();

and 

function() {
 ....
 ....
}();

Upvotes: 1

Views: 63

Answers (3)

Nick
Nick

Reputation: 156

They aren't really function signatures, they are Immediately-invoked function expressions (IIFE), and usually these are the two forms:

(function(){
/* ... */
})();

and

(function(){
/* ... */
}());

the parenthesis cause the function to be treated as a function expression. without them, the function will be treated as a function declaration

Upvotes: 0

marsh
marsh

Reputation: 1441

The first one is immediately invoked function, the second one is invalid JS, because when the parser encounters the function keyword, it find it as a function declaration, but not as a function expression.

For immediately invoked function best way is

(function(){ ... }());

or

(function(){ ... })();

But you can also prefixing the function with a unary operator, it will be save a byte

!function(){ ... }();
~function(){ ... }();
-function(){ ... }();
+function(){ ... }();

Upvotes: 0

mohamedrias
mohamedrias

Reputation: 18566

The first one is a Self Invoking Function.

(function(){
 ....
 ....
})();

The function will be invoked by itself. It's mostly used for wrapping the code inside to prevent the variables from polluting the global namespace.You can notice it in popular libraries such as jQuery.

Another use case of it is:

As javascript is function scoped language when compared to other languages which are usually block scoped. If you want to create local variables inside function you can use IIFE for that purpose as well.

The second one is actually a syntax error. But it can be like

(function(){
 ....
 ....
}());

It's another way of representing the self invoking function.

Upvotes: 1

Related Questions