freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/understand-the-immediately-invoked-function-expression-iife.md

---
id: 587d7db2367417b2b2512b8b
title: Understand the Immediately Invoked Function Expression (IIFE)
challengeType: 1
forumTopicId: 301328
dashedName: understand-the-immediately-invoked-function-expression-iife
---

# --description--

A common pattern in JavaScript is to execute a function as soon as it is declared:

```js
(function () {
  console.log("Chirp, chirp!");
})();
```

This is an anonymous function expression that executes right away, and outputs `Chirp, chirp!` immediately.

Note that the function has no name and is not stored in a variable. The two parentheses () at the end of the function expression cause it to be immediately executed or invoked. This pattern is known as an <dfn>immediately invoked function expression</dfn> or <dfn>IIFE</dfn>.

# --instructions--

Rewrite the function `makeNest` and remove its call so instead it's an anonymous immediately invoked function expression (IIFE).

# --hints--

The function should be anonymous.

```js
assert(/\((function|\(\))(=>|\(\)){?/.test(code.replace(/\s/g, '')));
```

Your function should have parentheses at the end of the expression to call it immediately.

```js
assert(/\(.*(\)\(|\}\(\))\)/.test(code.replace(/[\s;]/g, '')));
```

# --seed--

## --seed-contents--

```js
function makeNest() {
  console.log("A cozy nest is ready");
}

makeNest();
```

# --solutions--

```js
(function () {
  console.log("A cozy nest is ready");
})();
```

---

```js
(function () {
  console.log("A cozy nest is ready");
}());
```

---

```js
(() => {
  console.log("A cozy nest is ready");
})();
```

---

```js
(() =>
  console.log("A cozy nest is ready")
)();
```