javascript - Array.slice() 参数不是函数

Question

我在使用 freeCodeCamp beta 时遇到了一个奇怪的问题。

这样做的“目的”不是修改原始数组，而是使用函数式编程技术来修改数组。

但是，我不断收到关于“array”参数的提示，因为删除函数不是有效的函数:

//  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 (bookListTemp, bookName) {
  let newBookArr = bookListTemp;
  return newBookArr.push(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 (bookList,bookName) {
  let newArr = bookList.slice();
  if (newArr.indexOf(bookName) >= 0) {

    return newArr.slice(0, 1, bookName);

    // 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);

在删除函数中，我尝试获取参数并执行 array.slice() 方法以及 array.concat() 方法。因为执行 let newArr = bookList 实际上并没有使新数组正确吗？它只是创建了一个引用原始数组的新副本，正确吗？

我得到的确切错误是TypeError: bookList.slice is not a function

更奇怪的是Array.isArray(bookList)返回true(在函数remove中。所以我不明白为什么它是提示数组方法？

Answer 1

您的问题是Array.push

return The new length property of the object upon which the method was called.

你应该返回数组

function add (bookListTemp, bookName) {
      let newBookArr = bookListTemp;
      newBookArr.push(bookName);
      // Add your code above this line
      return newBookArr;
    }

或来试试Array.concat相反

function add (bookListTemp, bookName) {
  let newBookArr = bookListTemp;
  return newBookArr.concat(bookName);
  // Add your code above this line
}