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fix(curriculum): Rewrote the Write Higher-Order Arrow Functions challenge and moved to Functional Programming section (#35954)

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* fix: reworded and moved challenge

* fix: removed extra line

Co-Authored-By: RandellDawson <5313213+RandellDawson@users.noreply.github.com>

* fix; removed extra line

Co-Authored-By: RandellDawson <5313213+RandellDawson@users.noreply.github.com>

* fix: reworded sentence

Co-Authored-By: RandellDawson <5313213+RandellDawson@users.noreply.github.com>
This commit is contained in:
Randell Dawson
2019-05-15 09:12:17 -07:00
committed by Tom
parent d390b40a9f
commit 4b4762716c
5 changed files with 100 additions and 151 deletions
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guide/english/certifications/javascript-algorithms-and-data-structures/es6/write-higher-order-arrow-functions/index.md
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---
title: Write Higher Order Arrow Functions
---
![:triangular_flag_on_post:](https://forum.freecodecamp.com/images/emoji/emoji_one/triangular_flag_on_post.png?v=3 ":triangular_flag_on_post:") Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program ![:busts_in_silhouette:](https://forum.freecodecamp.com/images/emoji/emoji_one/busts_in_silhouette.png?v=3 ":busts_in_silhouette:") and write your own code ![:pencil:](https://forum.freecodecamp.com/images/emoji/emoji_one/pencil.png?v=3 ":pencil:")
### Problem explanation:
We need to compute and square values from the `realNumberArray` and store them in the variable `squaredIntegers` using the `map()`, `filter()`, and/or `reduce()` functions.
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1
* You will need to `filter()` the `realNumberArray` for positive integers (decimals are not integers).
> _try to solve the problem now_
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 2
* You will need to `map()` the values from your `filter()` function to the variable `squaredIntegers`.
> _try to solve the problem now_
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 3
* Remember the magic of chaining functions.
> _try to solve the problem now_
## Spoiler alert!
![warning sign](//discourse-user-assets.s3.amazonaws.com/original/2X/2/2d6c412a50797771301e7ceabd554cef4edcd74d.gif)
**Solution ahead!**
## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Code solution:
```javascript
const squareList = (arr) => {
"use strict";
const squaredIntegers = arr.filter((num) => num > 0 && num % parseInt(num) === 0).map((num) => Math.pow(num, 2));
return squaredIntegers;
};
// test your code
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);
```
- [Run code at codepen.io](https://codepen.io/dylantyates/pen/WyWoYJ)
### Code explanation:
Uses the operator `filter()` and `map()` functions to square all positive integers in a given array.
## Alternative code solution:
```javascript
// change code below this line
const squaredIntegers = arr.filter((param) => Number.isInteger(param) && param >= 0).map(x => x * x);
// change code above this line
```
- [Run code at repl.it](https://repl.it/@AdrianSkar/ES6-Write-higher-order-arrow-functions)
### Code explanation
This does basically the same but uses the `isInteger()` method to check the numbers.
### Resources
- ["Array.prototype.map()" - *MDN JavaScript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map)
- ["Array.prototype.filter()" - *MDN JavaScript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter)
- ["Array.prototype.reduce()" - *MDN JavaScript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce)
- ["Number.isInteger()" - *MDN JavaScript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger)
- ["Math.pow()" - *MDN JavaScript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/pow)