f1c9b08cf3
This includes certificates (where it does nothing), but does not include any translations.
85 lines
2.7 KiB
Markdown
85 lines
2.7 KiB
Markdown
---
|
|
id: cf1111c1c12feddfaeb1bdef
|
|
title: Generate Random Whole Numbers with JavaScript
|
|
challengeType: 1
|
|
isHidden: false
|
|
videoUrl: 'https://scrimba.com/c/cRn6bfr'
|
|
forumTopicId: 18186
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
It's great that we can generate random decimal numbers, but it's even more useful if we use it to generate random whole numbers.
|
|
<ol><li>Use <code>Math.random()</code> to generate a random decimal.</li><li>Multiply that random decimal by <code>20</code>.</li><li>Use another function, <code>Math.floor()</code> to round the number down to its nearest whole number.</li></ol>
|
|
Remember that <code>Math.random()</code> can never quite return a <code>1</code> and, because we're rounding down, it's impossible to actually get <code>20</code>. This technique will give us a whole number between <code>0</code> and <code>19</code>.
|
|
Putting everything together, this is what our code looks like:
|
|
<code>Math.floor(Math.random() * 20);</code>
|
|
We are calling <code>Math.random()</code>, multiplying the result by 20, then passing the value to <code>Math.floor()</code> function to round the value down to the nearest whole number.
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
Use this technique to generate and return a random whole number between <code>0</code> and <code>9</code>.
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: The result of <code>randomWholeNum</code> should be a whole number.
|
|
testString: assert(typeof randomWholeNum() === "number" && (function(){var r = randomWholeNum();return Math.floor(r) === r;})());
|
|
- text: You should be using <code>Math.random</code> to generate a random number.
|
|
testString: assert(code.match(/Math.random/g).length > 1);
|
|
- text: You should have multiplied the result of <code>Math.random</code> by 10 to make it a number that is between zero and nine.
|
|
testString: assert(code.match(/\s*?Math.random\s*?\(\s*?\)\s*?\*\s*?10[\D]\s*?/g) || code.match(/\s*?10\s*?\*\s*?Math.random\s*?\(\s*?\)\s*?/g));
|
|
- text: You should use <code>Math.floor</code> to remove the decimal part of the number.
|
|
testString: assert(code.match(/Math.floor/g).length > 1);
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='js-seed'>
|
|
|
|
```js
|
|
var randomNumberBetween0and19 = Math.floor(Math.random() * 20);
|
|
|
|
function randomWholeNum() {
|
|
|
|
// Only change code below this line
|
|
|
|
return Math.random();
|
|
}
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
### After Test
|
|
<div id='js-teardown'>
|
|
|
|
```js
|
|
(function(){return randomWholeNum();})();
|
|
```
|
|
|
|
</div>
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
|
|
```js
|
|
var randomNumberBetween0and19 = Math.floor(Math.random() * 20);
|
|
function randomWholeNum() {
|
|
return Math.floor(Math.random() * 10);
|
|
}
|
|
```
|
|
|
|
</section>
|