84 lines
2.7 KiB
Markdown
84 lines
2.7 KiB
Markdown
---
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id: cf1111c1c12feddfaeb1bdef
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title: Generate Random Whole Numbers with JavaScript
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cRn6bfr'
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forumTopicId: 18186
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---
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## Description
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<section id='description'>
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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.
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<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>
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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>.
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Putting everything together, this is what our code looks like:
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<code>Math.floor(Math.random() * 20);</code>
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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.
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</section>
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## Instructions
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<section id='instructions'>
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Use this technique to generate and return a random whole number between <code>0</code> and <code>9</code>.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: The result of <code>randomWholeNum</code> should be a whole number.
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testString: assert(typeof randomWholeNum() === "number" && (function(){var r = randomWholeNum();return Math.floor(r) === r;})());
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- text: You should be using <code>Math.random</code> to generate a random number.
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testString: assert(code.match(/Math.random/g).length > 1);
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- 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.
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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));
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- text: You should use <code>Math.floor</code> to remove the decimal part of the number.
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testString: assert(code.match(/Math.floor/g).length > 1);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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var randomNumberBetween0and19 = Math.floor(Math.random() * 20);
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function randomWholeNum() {
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// Only change code below this line.
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return Math.random();
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}
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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(function(){return randomWholeNum();})();
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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var randomNumberBetween0and19 = Math.floor(Math.random() * 20);
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function randomWholeNum() {
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return Math.floor(Math.random() * 10);
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}
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```
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</section>
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