FCC将全局变量从函数中重构出来，数组没有同时使用这两种方法

Question

通过新的FCC材料。肯定出了点问题。这个我已经接近了，但是它仍然是错误的，因为它没有通过最后的测试：

"newestBookList应等同于“巴斯克维尔猎犬”、“哲学家”、“亚里士多德研究”、“时间简史”

当我console.log(newestBookList)时，我看到它删除了正确的条目，但没有添加“简要历史”。有什么建议吗？我不清楚为什么这两种方法各自工作，但在这里不一起工作，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函数引用的是原始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，您可以考虑只检查一次indexOf：

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