为数组的每个值返回 NAN [关闭]答案

【问题标题】：Returning NAN for each value of array [closed]为数组的每个值返回 NAN [关闭]
【发布时间】：2020-07-14 16:01:18
【问题描述】：

我试图从我的数组中返回一个对象列表，但我返回的是三个 NAN 值。

var books = [];

function Book(title, author, alreadyRead){

    this.title = title
    this.author = author
    this.alreadyRead = alreadyRead

}

function addBook(title, author, alreadyRead){
    var b = new Book(title, author, alreadyRead);
    books.push(b);
}

addBook("The Hunger Games", "Suzannee Collins", true);
addBook("The Bible", "Various Authors", true);
addBook("The Hobbit", "J.R.R. Tolkien", false);

function printBooks(books){
    let arrayLength = books.length 

    for(let i = 0; i < arrayLength; i++){
        console.log(books.title + books.author);
    }
 }


 printBooks(books);

我不太确定发生了什么，所以谁能帮我解释一下？

【问题讨论】：

books.title + books.author - 变量 books 是 array，因此您尝试获取数组对象的属性 title 和属性 author把它们加在一起。 undefined + undefined 是 NaN。你想要books[i].title + books[i].author
console.log(books[i].title + books[i].author) — 你有索引变量，你只需要使用它

标签： javascript arrays nan

【解决方案1】：

你在 for 循环中缺少索引 [i]

function printBooks(books){
    let arrayLength = books.length 

    for(let i = 0; i < arrayLength; i++){
        console.log(books[i].title + books[i].author);
    }
 }

【讨论】：

【解决方案2】：

在printBooks 函数中，您使用for 遍历书籍属性，这意味着您必须指定书籍编号，即i -> 将是book[1].title = "The Hunger Games" 等等

我正在尝试从我的数组中返回一个对象列表

在你的函数中你只打印它们，这是你想要的吗？

var books = [];

function Book(title, author, alreadyRead) {

  this.title = title
  this.author = author
  this.alreadyRead = alreadyRead

}

function addBook(title, author, alreadyRead) {
  var b = new Book(title, author, alreadyRead);
  books.push(b);
}

addBook("The Hunger Games", "Suzannee Collins", true);
addBook("The Bible", "Various Authors", true);
addBook("The Hobbit", "J.R.R. Tolkien", false);

function printBooks(books) {
  let arrayLength = books.length

  for (let i = 0; i < arrayLength; i++) {
    console.log(books[i].title + books[i].author);
  }
}


printBooks(books);

【讨论】：