---
id: 587d8250367417b2b2512c5e
title: Learn how a Stack Works
challengeType: 1
videoUrl: ''
localeTitle: ''
---

## Description
undefined

## Instructions
undefined

## Tests
<section id='tests'>

```yml
tests:
  - text: ''
    testString: 'assert(homeworkStack.length === 4, "<code>homeworkStack</code> should only contain 4 elements.");'
  - text: ''
    testString: 'assert(homeworkStack[3] === "CS50", "The last element in <code>homeworkStack</code> should be <code>"CS50"</code>.");'
  - text: ''
    testString: 'assert(homeworkStack.indexOf("PSY44") === -1, "<code>homeworkStack</code> should not contain <code>"PSY44"</code>.");'
  - text: ''
    testString: 'assert(code.match(/=/g).length === 1 && /homeworkStack\s*=\s*\["BIO12"\s*,\s*"HIS80"\s*,\s*"MAT122"\s*,\s*"PSY44"\]/.test(code), "The initial declaration of the <code>homeworkStack</code> should not be changed.");'

```

</section>

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

<div id='js-seed'>

```js
var homeworkStack = ["BIO12","HIS80","MAT122","PSY44"];
// Only change code below this line

```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>