f1c9b08cf3
This includes certificates (where it does nothing), but does not include any translations.
110 lines
4.0 KiB
Markdown
110 lines
4.0 KiB
Markdown
---
|
|
id: 587d7b8e367417b2b2512b5c
|
|
title: Understand Functional Programming Terminology
|
|
challengeType: 1
|
|
isHidden: false
|
|
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
|
|
// Function that returns a string representing a cup of green tea
|
|
const prepareGreenTea = () => 'greenTea';
|
|
|
|
// Function that returns a string representing a cup of black tea
|
|
const prepareBlackTea = () => 'blackTea';
|
|
|
|
/*
|
|
Given a function (representing the tea type) and number of cups needed, the
|
|
following function returns an array of strings (each representing a cup of
|
|
a specific type of tea).
|
|
*/
|
|
const getTea = (prepareTea, numOfCups) => {
|
|
const teaCups = [];
|
|
|
|
for(let cups = 1; cups <= numOfCups; cups += 1) {
|
|
const teaCup = prepareTea();
|
|
teaCups.push(teaCup);
|
|
}
|
|
return teaCups;
|
|
};
|
|
|
|
// Only change code below this line
|
|
const tea4GreenTeamFCC = null;
|
|
const tea4BlackTeamFCC = null;
|
|
// Only change code above this line
|
|
|
|
console.log(
|
|
tea4GreenTeamFCC,
|
|
tea4BlackTeamFCC
|
|
);
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
```js
|
|
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>
|