freeCodeCamp/understand-functional-programming-terminology.md at dec409a4bd667e4979305cc1e86e0702bbc2c707

Oliver Eyton-Williams dec409a4bd fix: s/localeTitle/title/g

2020-10-06 23:10:08 +05:30

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id, challengeType, forumTopicId, title

id	challengeType	forumTopicId	title
587d7b8e367417b2b2512b5c	1	301240	了解函数式编程术语

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getTea函数来处理多种茶的请求。我们可以修改getTea接受一个函数作为参数，使它能够修改茶的类型。这让getTea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： Callbacks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filter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，这种函数叫做头等函数。在 JavaScript 中，所有函数都是头等函数。将函数为参数或返回值的函数叫做高阶函数。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lambda。

Instructions

准备 27 杯绿茶和 13 杯红茶，分别存入tea4GreenTeamFCC和tea4BlackTeamFCC变量。请注意，getTea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。

Tests

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');

Challenge Seed

/**
 * 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
);

Solution

// 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);

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