IIFE (Immediately-Invoked Function Expression in JavaScript)

#4 JavaScript Series

It is a JavaScript function that runs as soon as it is defined. It’s a design pattern also known as a self-executing anonymous function.

Here’s an example:

(
function () {
 console.log("Hello");
}
)();

You can also assign it to a variable for later use.

Usage:
- Avoids hoisting issues.
- Prevents global namespace pollution.
- Useful for creating modules.

@ Guess the Output

(
 function (x) {
     return (function(y){
         console.log(x+y);
     }
     )(2)
 }
)(1);

Output: 3

Explanation:
--------------
The outermost parentheses are used to wrap the entire function expression. This is a common practice to ensure the function is treated as an expression and not a declaration.

The outer function is immediately invoked with the argument 1. So, x inside the function becomes 1.

Inside the outer function, there's another immediately invoked function expression (function(y) { console.log(x + y); })(2). This inner function is immediately invoked with the argument 2.

Inside the inner function, y becomes 2. Then it calculates x + y, where x is from the outer function and y is from the inner function. So, x + y becomes 1 + 2, which is 3.

Finally, console.log(x + y) prints 3.