javascript - FCC 在函数之外重构全局变量，数组未同时使用这两种方法

Question

我正在研究新的 FCC Material 。肯定有部分问题。这个我已经接近了，但它仍然是错误的，因为它没有通过最终测试:

"newestBookList 应该等于 ["The Hound of the Baskervilles", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae", "A Brief History of Time"]"

当我使用 console.log(newestBookList) 时，我看到它删除了正确的条目但没有添加“Brief History”。有什么建议么？我不清楚为什么这两种方法在这里单独工作但不能一起工作，也不清楚如何使用 BDD 来测试...

// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function add(arr, bookName) {
  return arr.concat([bookName]);
}

  // Add your code above this line

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove(arr, bookName) {
  if (bookList.indexOf(bookName) >= 0) {
    var index = bookList.indexOf(bookName);
    return bookList.slice(0, index).concat(bookList.slice(index + 1));
    // Add your code above this line
  }
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
var newestBookList = remove(add(bookList, 'A Brief History of Time'), 'On The Electrodynamics of Moving Bodies');

//console.log(bookList);
//console.log(newBookList);
//console.log(newerBookList);
console.log(newestBookList);

Answer 1

您的remove 函数正在引用原始 bookList，而不是传递的数组。将所有 bookList 引用更改为 arr 引用(传递给 remove 函数的参数):

// the global variable
var bookList = ["The Hound of the Baskervilles", "On The Electrodynamics of Moving Bodies", "Philosophiæ Naturalis Principia Mathematica", "Disquisitiones Arithmeticae"];

/* This function should add a book to the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function add(arr, bookName) {
  return arr.concat([bookName]);
}

  // Add your code above this line

/* This function should remove a book from the list and return the list */
// New parameters should come before the bookName one

// Add your code below this line
function remove(arr, bookName) {
  if (arr.indexOf(bookName) >= 0) {
    var index = arr.indexOf(bookName);
    return arr.slice(0, index).concat(arr.slice(index + 1));
    // Add your code above this line
  } else console.log('n');
}

var newBookList = add(bookList, 'A Brief History of Time');
var newerBookList = remove(bookList, 'On The Electrodynamics of Moving Bodies');
const added = add(bookList, 'A Brief History of Time');
var newestBookList = remove(added, 'On The Electrodynamics of Moving Bodies');

//console.log(bookList);
// console.log(newBookList);
//console.log(newerBookList);
console.log(newestBookList);

不过，您可能会考虑只检查一次 indexOf:

function remove(arr, bookName) {
  var index = arr.indexOf(bookName);
  if (index === -1) return;
  return [...arr.slice(0, index), ...arr.slice(index + 1)];
}