72 lines
2.5 KiB
Markdown
72 lines
2.5 KiB
Markdown
|
---
|
||
|
|
id: bd7123c9c443eddfaeb5bdef
|
||
|
|
title: Declare JavaScript Variables
|
||
|
|
challengeType: 1
|
||
|
|
---
|
||
|
|
|
||
|
|
## Description
|
||
|
|
<section id='description'>
|
||
|
|
In computer science, <dfn>data</dfn> is anything that is meaningful to the computer. JavaScript provides seven different <dfn>data types</dfn> which are <code>undefined</code>, <code>null</code>, <code>boolean</code>, <code>string</code>, <code>symbol</code>, <code>number</code>, and <code>object</code>.
|
||
|
|
For example, computers distinguish between numbers, such as the number <code>12</code>, and <code>strings</code>, such as <code>"12"</code>, <code>"dog"</code>, or <code>"123 cats"</code>, which are collections of characters. Computers can perform mathematical operations on a number, but not on a string.
|
||
|
|
<dfn>Variables</dfn> allow computers to store and manipulate data in a dynamic fashion. They do this by using a "label" to point to the data rather than using the data itself. Any of the seven data types may be stored in a variable.
|
||
|
|
<code>Variables</code> are similar to the x and y variables you use in mathematics, which means they're a simple name to represent the data we want to refer to. Computer <code>variables</code> differ from mathematical variables in that they can store different values at different times.
|
||
|
|
We tell JavaScript to create or <dfn>declare</dfn> a variable by putting the keyword <code>var</code> in front of it, like so:
|
||
|
|
<blockquote>var ourName;</blockquote>
|
||
|
|
creates a <code>variable</code> called <code>ourName</code>. In JavaScript we end statements with semicolons.
|
||
|
|
<code>Variable</code> names can be made up of numbers, letters, and <code>$</code> or <code>_</code>, but may not contain spaces or start with a number.
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Instructions
|
||
|
|
<section id='instructions'>
|
||
|
|
Use the <code>var</code> keyword to create a variable called <code>myName</code>.
|
||
|
|
<strong>Hint</strong><br>Look at the <code>ourName</code> example if you get stuck.
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Tests
|
||
|
|
<section id='tests'>
|
||
|
|
|
||
|
|
```yml
|
||
|
|
- text: 'You should declare <code>myName</code> with the <code>var</code> keyword, ending with a semicolon'
|
||
|
|
testString: 'assert(/var\s+myName\s*;/.test(code), "You should declare <code>myName</code> with the <code>var</code> keyword, ending with a semicolon");'
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Challenge Seed
|
||
|
|
<section id='challengeSeed'>
|
||
|
|
|
||
|
|
<div id='js-seed'>
|
||
|
|
|
||
|
|
```js
|
||
|
|
// Example
|
||
|
|
var ourName;
|
||
|
|
|
||
|
|
// Declare myName below this line
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
### After Test
|
||
|
|
<div id='js-teardown'>
|
||
|
|
|
||
|
|
```js
|
||
|
|
console.info('after the test');
|
||
|
|
```
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Solution
|
||
|
|
<section id='solution'>
|
||
|
|
|
||
|
|
|
||
|
|
```js
|
||
|
|
var myName;
|
||
|
|
```
|
||
|
|
|
||
|
|
</section>
|