121 lines
3.8 KiB
Markdown
121 lines
3.8 KiB
Markdown
---
|
||
id: 587d7b8e367417b2b2512b5c
|
||
title: Understand Functional Programming Terminology
|
||
challengeType: 1
|
||
forumTopicId: 301240
|
||
localeTitle: 了解函数式编程术语
|
||
---
|
||
|
||
## Description
|
||
<section id='description'>
|
||
FCC 团队需求有变更，现在想要两种茶：绿茶（green tea）和红茶（black tea）。事实证明，用户需求变更是很常见的。
|
||
基于以上信息，我们需要重构上一节挑战中的<code>getTea</code>函数来处理多种茶的请求。我们可以修改<code>getTea</code>接受一个函数作为参数，使它能够修改茶的类型。这让<code>getTea</code>更灵活，也使需求变更时为程序员提供更多控制权。
|
||
首先，我们将介绍一些术语：
|
||
<code>Callbacks</code>是被传递到另一个函数中调用的函数。你应该已经在其他函数中看过这个写法，例如在<code>filter</code>中，回调函数告诉 JavaScript 以什么规则过滤数组。
|
||
函数就像其他正常值一样，可以赋值给变量、传递给另一个函数，或从其它函数返回，这种函数叫做<code>头等</code>函数。在 JavaScript 中，所有函数都是<code>头等</code>函数。
|
||
将函数为参数或返回值的函数叫做<code>高阶</code>函数。
|
||
当函数传递给另一个函数或从另一个函数返回时，那些传入或返回的函数可以叫做<code>lambda</code>。
|
||
</section>
|
||
|
||
## Instructions
|
||
<section id='instructions'>
|
||
准备 27 杯绿茶和 13 杯红茶，分别存入<code>tea4GreenTeamFCC</code>和<code>tea4BlackTeamFCC</code>变量。请注意，<code>getTea</code>函数已经变了，现在它接收一个函数作为第一个参数。
|
||
注意：数据（茶的数量）作为最后一个参数。我们将在后面的课程中对此进行更多讨论。
|
||
</section>
|
||
|
||
## Tests
|
||
<section id='tests'>
|
||
|
||
```yml
|
||
tests:
|
||
- text: <code>tea4GreenTeamFCC</code>变量应存有为团队准备的 27 杯茶。
|
||
testString: assert(tea4GreenTeamFCC.length === 27);
|
||
- text: <code>tea4GreenTeamFCC</code>变量应存有绿茶。
|
||
testString: assert(tea4GreenTeamFCC[0] === 'greenTea');
|
||
- text: <code>tea4BlackTeamFCC</code>变量应存有 13 杯红茶。
|
||
testString: assert(tea4BlackTeamFCC.length === 13);
|
||
- text: <code>tea4BlackTeamFCC</code>变量应存有红茶。
|
||
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>
|