ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
113 lines
3.2 KiB
Markdown
113 lines
3.2 KiB
Markdown
---
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id: 587d7b8e367417b2b2512b5c
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title: 了解函数式编程术语
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challengeType: 1
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forumTopicId: 301240
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dashedName: understand-functional-programming-terminology
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---
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# --description--
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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。
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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。
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首先，我们将介绍一些术语：
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`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。
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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。
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将函数为参数或返回值的函数叫做`高阶`函数。
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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`。
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# --instructions--
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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。
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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。
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# --hints--
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`tea4GreenTeamFCC`变量应存有为团队准备的 27 杯茶。
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```js
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assert(tea4GreenTeamFCC.length === 27);
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```
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`tea4GreenTeamFCC`变量应存有绿茶。
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```js
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assert(tea4GreenTeamFCC[0] === 'greenTea');
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```
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`tea4BlackTeamFCC`变量应存有 13 杯红茶。
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```js
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assert(tea4BlackTeamFCC.length === 13);
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```
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`tea4BlackTeamFCC`变量应存有红茶。
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```js
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assert(tea4BlackTeamFCC[0] === 'blackTea');
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```
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# --seed--
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## --seed-contents--
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```js
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// Function that returns a string representing a cup of green tea
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const prepareGreenTea = () => 'greenTea';
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// Function that returns a string representing a cup of black tea
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const prepareBlackTea = () => 'blackTea';
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/*
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Given a function (representing the tea type) and number of cups needed, the
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following function returns an array of strings (each representing a cup of
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a specific type of tea).
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*/
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const getTea = (prepareTea, numOfCups) => {
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const teaCups = [];
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for(let cups = 1; cups <= numOfCups; cups += 1) {
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const teaCup = prepareTea();
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teaCups.push(teaCup);
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}
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return teaCups;
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};
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// Only change code below this line
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const tea4GreenTeamFCC = null;
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const tea4BlackTeamFCC = null;
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// Only change code above this line
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console.log(
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tea4GreenTeamFCC,
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tea4BlackTeamFCC
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);
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```
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# --solutions--
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```js
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const prepareGreenTea = () => 'greenTea';
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const prepareBlackTea = () => 'blackTea';
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const getTea = (prepareTea, numOfCups) => {
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const teaCups = [];
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for(let cups = 1; cups <= numOfCups; cups += 1) {
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const teaCup = prepareTea();
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teaCups.push(teaCup);
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}
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return teaCups;
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};
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const tea4BlackTeamFCC = getTea(prepareBlackTea, 13);
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const tea4GreenTeamFCC = getTea(prepareGreenTea, 27);
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```
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