freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/write-reusable-javascript-with-functions.english.md

---
id: 56bbb991ad1ed5201cd392cf
title: Write Reusable JavaScript with Functions
challengeType: 1
videoUrl: 'https://scrimba.com/c/cL6dqfy'
---

## Description
<section id='description'>
In JavaScript, we can divide up our code into reusable parts called <dfn>functions</dfn>.
Here's an example of a function:

```js
function functionName() {
  console.log("Hello World");
}
```

You can call or <dfn>invoke</dfn> this function by using its name followed by parentheses, like this:
<code>functionName();</code>
Each time the function is called it will print out the message <code>"Hello World"</code> on the dev console. All of the code between the curly braces will be executed every time the function is called.
</section>

## Instructions
<section id='instructions'>
<ol><li>Create a function called <code>reusableFunction</code> which prints <code>"Hi World"</code> to the dev console.</li><li>Call the function.</li></ol>
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>reusableFunction</code> should be a function
    testString: assert(typeof reusableFunction === 'function', '<code>reusableFunction</code> should be a function');
  - text: <code>reusableFunction</code> should output "Hi World" to the dev console
    testString: assert(hiWorldWasLogged, '<code>reusableFunction</code> should output "Hi World" to the dev console');
  - text: Call <code>reusableFunction</code> after you define it
    testString: assert(/^\s*reusableFunction\(\)\s*/m.test(code), 'Call <code>reusableFunction</code> after you define it');

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
// Example
function ourReusableFunction() {
  console.log("Heyya, World");
}

ourReusableFunction();

// Only change code below this line

```

</div>

### Before Test
<div id='js-setup'>

```js
var logOutput = "";
var originalConsole = console;
var nativeLog = console.log;
var hiWorldWasLogged = false;
function capture() {
    console.log = function (message) {
        if(message === 'Hi World')  hiWorldWasLogged = true;
        if(message && message.trim) logOutput = message.trim();
        if(nativeLog.apply) {
          nativeLog.apply(originalConsole, arguments);
        } else {
          var nativeMsg = Array.prototype.slice.apply(arguments).join(' ');
          nativeLog(nativeMsg);
        }
    };
}

function uncapture() {
  console.log = nativeLog;
}

capture();
```

</div>

### After Test
<div id='js-teardown'>

```js
uncapture();

if (typeof reusableFunction !== "function") { 
  (function() { return "reusableFunction is not defined"; })();
} else {
  (function() { return logOutput || "console.log never called"; })();
}
```

</div>

</section>

## Solution
<section id='solution'>


```js
function reusableFunction() {
  console.log("Hi World");
}
reusableFunction();
```

</section>