选择使用javascript es5更新或推送到数组

Question

I am trying to push an object into an array of objects but only if the particular object is not present in the array. If it is present the object should be updated.

I am required to do this with es5

Below is what I have tried

var database = require('../../database');
var autoincrementId = require('../../helpers/autoincrement-id');
var books = database.Books;

function Book(title, author, summary) {
  this.title = title;
  this.author = author;
  this.summary = summary;
}

Book.prototype.createBook = function () {
  var id = autoincrementId(id, database.Books); //autoincrement database id
  var copies = 1;
  var title = this.title.toLowerCase(), author = 
this.author.toLowerCase(), summary = this.summary.toLowerCase();
  if (!books.length) {
    books.push({id: id, title: title, author: author, summary: summary, copies: copies});
  } else {
     for(var book in books) {
      if(books[book].title === title) {
        books[book].copies += 1;
       break;
      }
      books.push({id: id, title: title, author: author, summary: summary, copies: copies});
    }
  }
};

But when i run the following

var abook = new Book('J', 'k', 'l');
var bbook = new Book('M', 'N', 'o');
abook.createBook();
abook.createBook();
bbook.createBook();
bbook.createBook();

console.log(books);

I get the following

[ { id: 1, title: 'j', author: 'k', summary: 'l', copies: 2 },
  { id: 2, title: 'm', author: 'n', summary: 'o', copies: 2 },
  { id: 3, title: 'm', author: 'n', summary: 'o', copies: 1 } ]

Instead of

[ { id: 1, title: 'j', author: 'k', summary: 'l', copies: 2 },
  { id: 2, title: 'm', author: 'n', summary: 'o', copies: 2 }]

Can someone please help me understand the problem with this code. Why does it update and insert at the second time and how can i solve this?

Answer 1

In your for(var book in books) { loop, you are checking if the current book is equal to the new one, then, if it's not the case, you add it. if the book is actually the second one of the list, it will be added since the first book checked isn't the new one. You might need a flag to ensure that no book was found :

var BookNotFound = true; // by default, no book found
for(var book in books) {
    if(books[book].title === title) {
        books[book].copies += 1;
        BookNotFound = false; // <------- a book was found
        break;
    }
}
// Outside of the loop :
if (BookNotFound)
    books.push({id: id, title: title, author: author, summary: summary, copies: copies});