87 lines
5.0 KiB
Markdown
87 lines
5.0 KiB
Markdown
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---
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id: 587d7b8f367417b2b2512b60
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title: Refactor Global Variables Out of Functions
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challengeType: 1
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videoUrl: ''
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localeTitle: 重构函数的全局变量
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---
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## Description
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<section id="description">到目前为止，我们已经看到了函数式编程的两个不同原则：1）不要改变变量或对象 - 创建新的变量和对象，并在需要时从函数返回它们。 2）声明函数参数 - 函数内的任何计算仅依赖于参数，而不依赖于任何全局对象或变量。在数字中添加一个并不是很令人兴奋，但我们可以在处理数组或更复杂的对象时应用这些原则。 </section>
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## Instructions
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<section id="instructions">重构（重写）代码，以便在任一函数内部不更改全局数组<code>bookList</code> 。 <code>add</code>函数应该将给定的<code>bookName</code>添加到数组的末尾。 <code>remove</code>函数应该从数组中删除给定的<code>bookName</code> 。这两个函数都应该返回一个数组，并且应该在<code>bookName</code>之前添加任何新参数。 </section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: '<code>bookList</code>不应该改变并且仍然相等<code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code> 。'
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testString: 'assert(JSON.stringify(bookList) === JSON.stringify(["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]), "<code>bookList</code> should not change and still equal <code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code>.");'
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- text: '<code>newBookList</code>应该等于<code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code> 。'
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testString: 'assert(JSON.stringify(newBookList) === JSON.stringify(["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]), "<code>newBookList</code> should equal <code>["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code>.");'
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- text: '<code>newerBookList</code>应该等于<code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code> 。'
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testString: 'assert(JSON.stringify(newerBookList) === JSON.stringify(["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]), "<code>newerBookList</code> should equal <code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"]</code>.");'
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- text: '<code>newestBookList</code>应该等于<code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code> 。'
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testString: 'assert(JSON.stringify(newestBookList) === JSON.stringify(["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]), "<code>newestBookList</code> should equal <code>["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]</code>.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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// the global variable
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var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];
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/* This function should add a book to the list and return the list */
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// New parameters should come before the bookName one
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// Add your code below this line
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function add (bookName) {
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return bookList.push(bookName);
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// Add your code above this line
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}
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/* This function should remove a book from the list and return the list */
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// New parameters should come before the bookName one
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// Add your code below this line
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function remove (bookName) {
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if (bookList.indexOf(bookName) >= 0) {
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return bookList.splice(0, 1, bookName);
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// Add your code above this line
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}
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}
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var newBookList = add(bookList, 'A Brief History of Time');
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var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
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var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');
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console.log(bookList);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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