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
3.6 KiB
Markdown
113 lines
3.6 KiB
Markdown
---
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id: 587d7b8e367417b2b2512b5c
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title: Understand Functional Programming Terminology
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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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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.
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With that information, we'll need to revisit the `getTea` function from last challenge to handle various tea requests. We can modify `getTea` to accept a function as a parameter to be able to change the type of tea it prepares. This makes `getTea` more flexible, and gives the programmer more control when client requests change.
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But first, let's cover some functional terminology:
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<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 `filter`, the callback function tells JavaScript the criteria for how to filter an array.
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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.
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The functions that take a function as an argument, or return a function as a return value are called <dfn>higher order</dfn> functions.
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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>.
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# --instructions--
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Prepare 27 cups of green tea and 13 cups of black tea and store them in `tea4GreenTeamFCC` and `tea4BlackTeamFCC` variables, respectively. Note that the `getTea` function has been modified so it now takes a function as the first argument.
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Note: The data (the number of cups of tea) is supplied as the last argument. We'll discuss this more in later lessons.
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# --hints--
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The `tea4GreenTeamFCC` variable should hold 27 cups of green tea for the team.
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```js
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assert(tea4GreenTeamFCC.length === 27);
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```
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The `tea4GreenTeamFCC` variable should hold cups of green tea.
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```js
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assert(tea4GreenTeamFCC[0] === 'greenTea');
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```
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The `tea4BlackTeamFCC` variable should hold 13 cups of black tea.
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```js
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assert(tea4BlackTeamFCC.length === 13);
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```
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The `tea4BlackTeamFCC` variable should hold cups of black tea.
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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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