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

* 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>
2019-05-15 09:12:17 -07:00
parent d390b40a9f
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--- a/guide/english/certifications/javascript-algorithms-and-data-structures/functional-programming/use-higher-order-functions-map-filter-or-reduce-to-solve-a-complex-problem/index.md
+++ b/guide/english/certifications/javascript-algorithms-and-data-structures/functional-programming/use-higher-order-functions-map-filter-or-reduce-to-solve-a-complex-problem/index.md
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+---
+title: Use Higher-Order Functions map, filter, or reduce to Solve a Complex Problem 
+---
+![: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:
+```js
+const squareList = (arr) => arr
+  .filter((num) => num > 0 && num % parseInt(num) === 0)
+  .map((num) => Math.pow(num, 2));
+```
+
+### Code explanation:
+
+Uses the operator `filter()` and `map()` functions to square all positive integers in a given array.
+
+## Alternative code solution:
+```js
+const squareList = (arr) => {
+  return arr.reduce((sqrIntegers, num) => {
+    return Number.isInteger(num) && num > 0
+      ? sqrIntegers.concat(num * num)
+      : sqrIntegers;
+  }, []);
+};
+```
+
+### 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)