JavaScript Interview Question #103

What is an IIFE in JavaScript?

Closures, Prototypes, Classes & Advanced Functions Mid-Level Intermediate

Quick Interview Answer

An IIFE, or Immediately Invoked Function Expression, is a function expression that executes immediately after it is created. Before ES modules and block-scoped declarations became common, IIFEs were frequently used to create a private scope and avoid leaking variables into the global scope.

Detailed Explanation

IIFEs still appear in existing code and can be useful for one-time initialization, although modules and block scope now solve many of the same organizational problems more directly.

Code Example

(function () {
    const message = "Initialized privately";
    console.log(message);
})();

(() => {
    console.log("Arrow-function IIFE");
})();