Javascript function with an “!”

Have you ever encountered this line of code in Javascript and wonder what this means?

! function () {
  //Some code
}();

It’s actually another way of writing a self-invoking function or self-executing function.

Self-invoking functions are functions that automatically call itself without the need of invoking it.

You can create a self-invoking function by enclosing your function in a parenthesis and add the () after your function.

(function () {
    //Some code
})();

Or as explain above use ! in exchange of ().

If you are new to functions or you just want to see how this self-invoking functions evolved in it’s syntax from a basic function, continue reading on….

FUNCTION is a block of code that does a particular task or action.

A function can be declared in the following way:

1. Anonymous Function Expression:

function () {
  //Some code 
};

2. Named Function Expression:

function name() {
   //Some code 
};

A function is used in the following way:

To use the anonymous functions, most of the time we try to pass it first into a variable:

var name = function () {
   //Some code
};
// To call/use it, type the name of the variable and add the () on the end.
name();

To use the named functions:

function name() {
   //Some code 
};
//To call/use it, just type the function name in with the ();
name();

Now if you want to trigger the function right away without calling it, we use the self-invoking function (self-executing function) as discussed above. But i’ll discuss it again so you won’t need to go up….

Self-invoking or self-executing functions:

// You need to wrap the function into a parenthesis first, then add the () after the close parenthesis to call it right away.
(function () {
    //Some code
})();

Or instead of using the parethesis, we can use the “!”

// ! in exchange of the ()
! function () {
//Some code
}();

NOTE: There are also functions with parameters inside it. These are just examples of functions without parameters to easily explain what is a self-invoking function and its syntax.

If this lesson has helped you in anyway, you can give it a ❤ or share it out. Thanks! :)