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SomeDer bfa5c26288 fix: use dfn instead of code tag ()
* Use dfn tags

* remove misused <dfn> tags

* Revert "remove misused <dfn> tags"

This reverts commit b24968a968.

* Update curriculum/challenges/english/01-responsive-web-design/basic-html-and-html5/fill-in-the-blank-with-placeholder-text.english.md

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

* Make "array" lowercase

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

* Fix dfn usage

* Address last dfn tags
2019-10-27 12:45:37 -04:00

120 lines
4.1 KiB
Markdown

---
id: 587d7b8e367417b2b2512b5c
title: Understand Functional Programming Terminology
challengeType: 1
forumTopicId: 301240
---
## Description
<section id='description'>
The FCC Team had a mood swing and now wants two types of tea: green tea and black tea. General Fact: Client mood swings are pretty common.
With that information, we'll need to revisit the <code>getTea</code> function from last challenge to handle various tea requests. We can modify <code>getTea</code> to accept a function as a parameter to be able to change the type of tea it prepares. This makes <code>getTea</code> more flexible, and gives the programmer more control when client requests change.
But first, let's cover some functional terminology:
<dfn>Callbacks</dfn> are the functions that are slipped or passed into another function to decide the invocation of that function. You may have seen them passed to other methods, for example in <code>filter</code>, the callback function tells JavaScript the criteria for how to filter an array.
Functions that can be assigned to a variable, passed into another function, or returned from another function just like any other normal value, are called <dfn>first class</dfn> functions. In JavaScript, all functions are first class functions.
The functions that take a function as an argument, or return a function as a return value are called <dfn>higher order</dfn> functions.
When the functions are passed in to another function or returned from another function, then those functions which gets passed in or returned can be called a <dfn>lambda</dfn>.
</section>
## Instructions
<section id='instructions'>
Prepare 27 cups of green tea and 13 cups of black tea and store them in <code>tea4GreenTeamFCC</code> and <code>tea4BlackTeamFCC</code> variables, respectively. Note that the <code>getTea</code> function has been modified so it now takes a function as the first argument.
Note: The data (the number of cups of tea) is supplied as the last argument. We'll discuss this more in later lessons.
</section>
## Tests
<section id='tests'>
```yml
tests:
- text: The <code>tea4GreenTeamFCC</code> variable should hold 27 cups of green tea for the team.
testString: assert(tea4GreenTeamFCC.length === 27);
- text: The <code>tea4GreenTeamFCC</code> variable should hold cups of green tea.
testString: assert(tea4GreenTeamFCC[0] === 'greenTea');
- text: The <code>tea4BlackTeamFCC</code> variable should hold 13 cups of black tea.
testString: assert(tea4BlackTeamFCC.length === 13);
- text: The <code>tea4BlackTeamFCC</code> variable should hold cups of black tea.
testString: assert(tea4BlackTeamFCC[0] === 'blackTea');
```
</section>
## Challenge Seed
<section id='challengeSeed'>
<div id='js-seed'>
```js
/**
* A long process to prepare green tea.
* @return {string} A cup of green tea.
**/
const prepareGreenTea = () => 'greenTea';
/**
* A long process to prepare black tea.
* @return {string} A cup of black tea.
**/
const prepareBlackTea = () => 'blackTea';
/**
* Get given number of cups of tea.
* @param {function():string} prepareTea The type of tea preparing function.
* @param {number} numOfCups Number of required cups of tea.
* @return {Array<string>} Given amount of tea cups.
**/
const getTea = (prepareTea, numOfCups) => {
const teaCups = [];
for(let cups = 1; cups <= numOfCups; cups += 1) {
const teaCup = prepareTea();
teaCups.push(teaCup);
}
return teaCups;
};
// Add your code below this line
const tea4GreenTeamFCC = null; // :(
const tea4BlackTeamFCC = null; // :(
// Add your code above this line
console.log(
tea4GreenTeamFCC,
tea4BlackTeamFCC
);
```
</div>
</section>
## Solution
<section id='solution'>
```js
// solution required
const prepareGreenTea = () => 'greenTea';
const prepareBlackTea = () => 'blackTea';
const getTea = (prepareTea, numOfCups) => {
const teaCups = [];
for(let cups = 1; cups <= numOfCups; cups += 1) {
const teaCup = prepareTea();
teaCups.push(teaCup);
}
return teaCups;
};
const tea4BlackTeamFCC = getTea(prepareBlackTea, 13);
const tea4GreenTeamFCC = getTea(prepareGreenTea, 27);
```
</section>