4.4 KiB
id, title, challengeType, forumTopicId, dashedName
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
587d7b8f367417b2b2512b60 | 在函數中重構全局變量 | 1 | 301235 | refactor-global-variables-out-of-functions |
--description--
目前爲止,我們已經看到了函數式編程的兩個原則:
-
不要更改變量或對象 - 創建新變量和對象,並在需要時從函數返回它們。 提示:使用類似
const newArr = arrVar
的東西,其中arrVar
是一個數組,只會創建對現有變量的引用,而不是副本。 所以更改newArr
中的值會同時更改arrVar
中的值。 -
聲明函數參數 - 函數內的任何計算僅取決於參數,而不取決於任何全局對象或變量。
給數字增加 1 不夠刺激,我們可以在處理數組或更復雜的對象時應用這些原則。
--instructions--
重構代碼,使全局數組 bookList
在函數內部不會被改變。 add
函數可以將指定的 bookName
增加到數組末尾並返回一個新的數組(列表)。 remove
函數可以從數組中移除指定 bookName
。
注意: 兩個函數都應該返回一個數組,任何新參數都應該在 bookName
參數之前添加。
--hints--
bookList
應等於 ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]
.
add(bookList, "Test");
remove(bookList, "The Hound of the Baskervilles");
assert(
JSON.stringify(bookList) ===
JSON.stringify([
'The Hound of the Baskervilles',
'On The Electrodynamics of Moving Bodies',
'Philosophiæ Naturalis Principia Mathematica',
'Disquisitiones Arithmeticae'
])
);
add(bookList, "A Brief History of Time")
應該返回 ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]
。
assert(
JSON.stringify(add(bookList, "A Brief History of Time")) ===
JSON.stringify([
'The Hound of the Baskervilles',
'On The Electrodynamics of Moving Bodies',
'Philosophiæ Naturalis Principia Mathematica',
'Disquisitiones Arithmeticae',
'A Brief History of Time'
])
);
remove(bookList, "On The Electrodynamics of Moving Bodies")
應該返回 ["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]
。
assert(
JSON.stringify(remove(bookList, 'On The Electrodynamics of Moving Bodies')) ===
JSON.stringify([
'The Hound of the Baskervilles',
'Philosophiæ Naturalis Principia Mathematica',
'Disquisitiones Arithmeticae'
])
);
remove(add(bookList, "A Brief History of Time"), "On The Electrodynamics of Moving Bodies");
應該返回 ["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]
。
assert(
JSON.stringify(remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies')) ===
JSON.stringify([
'The Hound of the Baskervilles',
'Philosophiæ Naturalis Principia Mathematica',
'Disquisitiones Arithmeticae',
'A Brief History of Time'
])
);
--seed--
--seed-contents--
// The global variable
const bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];
// Change code below this line
function add(bookName) {
bookList.push(bookName);
return bookList;
// Change code above this line
}
// Change code below this line
function remove(bookName) {
const book_index = bookList.indexOf(bookName);
if (book_index >= 0) {
bookList.splice(book_index, 1);
return bookList;
// Change code above this line
}
}
--solutions--
// The global variable
const bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];
function add(bookList, bookName) {
return [...bookList, bookName];
}
function remove(bookList, bookName) {
const bookListCopy = [...bookList];
const bookNameIndex = bookList.indexOf(bookName);
if (bookNameIndex >= 0) {
bookListCopy.splice(bookNameIndex, 1);
}
return bookListCopy;
}