JavaScript does not support the enumeration of programs

Question

JavaScript does not support the enumeration of programs

I'm currently working on a program that takes user input (library, authorName) and displays the titles of books written by the author.

Here is an example library structure:

let library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

This is my code snippet:

let library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

function searchBooks(library, author) {
  for (author in library) { //enumerate
    if (author in library) {
      let line = Object.values(library[0]) // find line of the wanted author
      let result = (line[0] + "," + line[1]) // store author name and title name
      return result
    } else {
      return "NOT FOUND"
    }
  }
}

console.log(searchBooks(library, 'Bill Gates'))

The output generated looks like this: Bill Gates,The Road Ahead

The challenge: Regardless of which author I input into the searchBook, it always returns Bill Gates as the first entry in the library. It seems to not be iterating through all entries. Why might this be happening?

Initially, I thought about avoiding hard coding [0] and [1] and instead using i and i++. However, this approach resulted in a

TypeError: Cannot convert undefined or null to object

error message.

javascript enumeration

Answer 1

Answer №1

Here are a few key points to keep in mind:

Instead of using for (author in library), consider using of which evaluates each value in the array. In this case, we're naming that value book.
It's advisable to make your result an array or collection so that you can easily store multiple responses.
When checking for the author in the library object, use book.author == author to ensure that the author is a value of the object's author key.
Since the result is an array, join the values with a newline. If the result array is empty (falsey), return the NOT FOUND message. Otherwise, return all the books.

let library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

function searchBooks(library, author) {
  let result = []

  for (let book of library) {
    if (book.author == author) {
      let line = Object.values(book)
      result.push(line[0] + "," + line[1])
    }
  }

  return result.join('\n') || 'NOT FOUND'
}

console.log(1, searchBooks(library, 'Carolann Camilo'))
console.log(2, searchBooks(library, 'Bill Gates'))
console.log(3, searchBooks(library, 'Oh boy'))

Note:

To avoid using Object.values, refer to this explanation.
If you want to filter specific books from the library, consider using filter. Check out this solution.
Another approach to iterating over the library is by using forEach. Learn more about it from this answer.

Answer 2

Here are a few key points to keep in mind:

Instead of using for (author in library), consider using of which evaluates each value in the array. In this case, we're naming that value book.
It's advisable to make your result an array or collection so that you can easily store multiple responses.
When checking for the author in the library object, use book.author == author to ensure that the author is a value of the object's author key.
Since the result is an array, join the values with a newline. If the result array is empty (falsey), return the NOT FOUND message. Otherwise, return all the books.

let library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

function searchBooks(library, author) {
  let result = []

  for (let book of library) {
    if (book.author == author) {
      let line = Object.values(book)
      result.push(line[0] + "," + line[1])
    }
  }

  return result.join('\n') || 'NOT FOUND'
}

console.log(1, searchBooks(library, 'Carolann Camilo'))
console.log(2, searchBooks(library, 'Bill Gates'))
console.log(3, searchBooks(library, 'Oh boy'))

Note:

To avoid using Object.values, refer to this explanation.
If you want to filter specific books from the library, consider using filter. Check out this solution.
Another approach to iterating over the library is by using forEach. Learn more about it from this answer.

Answer 3

Answer №2

If you're looking to filter through an array in JavaScript, consider using the Array.filter method (check out MDN for more info):

const library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

console.log(findAuthor(library, `Bill Gates`));

function findAuthor(library, author) {
  return library.filter(book => book.author === author);
}

Answer 4

If you're looking to filter through an array in JavaScript, consider using the Array.filter method (check out MDN for more info):

const library = [
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
  { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
  { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

console.log(findAuthor(library, `Bill Gates`));

function findAuthor(library, author) {
  return library.filter(book => book.author === author);
}

Answer 5

Answer №3

Using the forEach method, you can iterate through elements and compile multiple entries by the same author into a given result.


let bookshelf = [
  {author: 'J.K. Rowling', title: 'Harry Potter and the Sorcerer\'s Stone', libraryID: 1234 },
  { author: 'Stephen King', title: 'The Shining', libraryID: 5678 },
  { author: 'J.K. Rowling', title: 'Harry Potter and the Chamber of Secrets', libraryID: 9012 }
];
function findBooks(library, author) {
  let result = ""
  library.forEach(book => {
    if (book.author === author) {
      result += book.author+", "+book.title+"\n"
    }
  })
  return result
}

console.log(findBooks(bookshelf, "J.K. Rowling"))

Answer 6

Using the forEach method, you can iterate through elements and compile multiple entries by the same author into a given result.


let bookshelf = [
  {author: 'J.K. Rowling', title: 'Harry Potter and the Sorcerer\'s Stone', libraryID: 1234 },
  { author: 'Stephen King', title: 'The Shining', libraryID: 5678 },
  { author: 'J.K. Rowling', title: 'Harry Potter and the Chamber of Secrets', libraryID: 9012 }
];
function findBooks(library, author) {
  let result = ""
  library.forEach(book => {
    if (book.author === author) {
      result += book.author+", "+book.title+"\n"
    }
  })
  return result
}

console.log(findBooks(bookshelf, "J.K. Rowling"))

Answer 7

Answer №4

Below is a functional version of the method you've proposed:

let library = [
    { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
    { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
    { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

function searchBooks(library, author) {
    for (const book of library) { //browse through
        if (book.author === author) {
            let result = (book.author + "," + book.title) // save author and title
            return result
        }
    }
    return 'NOT FOUND'
}

console.log(searchBooks(library, 'Bill Gates'))

Start by looping through the books in the library, not just the authors.
Determine if the author of the book matches the desired author.
Then display the author and title of that book separated by a comma.

Keep in mind this will only provide the first match found, not all matches.

Answer 8

Below is a functional version of the method you've proposed:

let library = [
    { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254 },
    { author: 'Carolann Camilo', title: 'Eyewitness', libraryID: 32456 },
    { author: 'Carolann Camilo', title: 'Cocky Marine', libraryID: 32457 }
];

function searchBooks(library, author) {
    for (const book of library) { //browse through
        if (book.author === author) {
            let result = (book.author + "," + book.title) // save author and title
            return result
        }
    }
    return 'NOT FOUND'
}

console.log(searchBooks(library, 'Bill Gates'))

Start by looping through the books in the library, not just the authors.
Determine if the author of the book matches the desired author.
Then display the author and title of that book separated by a comma.

Keep in mind this will only provide the first match found, not all matches.

JavaScript does not support the enumeration of programs

Answer №1

Answer №2

Answer №3

Answer №4

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