Is this a more effective solution to the second challenge in this lesson?

Question

The second challenge in the lesson calls for a final array of all the book titles contained in the array "users".
javascript
const users = [
  {
    name: 'Samir',
    age: 27,
    favoriteBooks:[
      {title: 'The Iliad'},
      {title: 'The Brothers Karamazov'}
    ]
  },
  {
    name: 'Angela',
    age: 33,
    favoriteBooks:[
      {title: 'Tenth of December'},
      {title: 'Cloud Atlas'},
      {title: 'One Hundred Years of Solitude'}
    ]
  },
  {
    name: 'Beatrice',
    age: 42,
    favoriteBooks:[
      {title: 'Candide'}
    ]
  }
];

The result should be:
javascript
['The Iliad', 'The Brothers Karamazov', 'Tenth of December', 'Cloud Atlas', 'One Hundred Years of Solitude', 'Candide'];

The solution covered in the lesson uses the map method twice (the second map method is used inside the first map method) and then reduces the book arrays into one array with all the book titles.
```javascript
const books = users
    .map(user => user.favoriteBooks.map(book => book.title))
    .reduce((arr, titles) => [...arr, ...titles], []);
console.log(books);
```
Wouldn't it be more effective if we first use the reduce method on the array, and then chain the map method afterwards?
By reducing first, the map method only needs to be used once.
```javascript
const books = users
    .reduce((arr, users) => [...arr, ...user.favoriteBooks], [])
    .map(book => book.title);
console.log(books);
```

Steven Parker · Answer

Sometimes the examples aren't the absolutely most concise or efficient solutions, but then the objective is to illustrate the principles and methods of the lesson.
Plus, that allows for the fun of optimizing it further.  And a quick benchmark test shows that you improved the efficiency of the solution by about 26%.  Good job!  :+1:

Brenden Seidel · Answer

Was wondering the same thing! I did similar to your solution, but just put the map in the reduce callback:
javascript
const books = users.reduce((arr, user) => [...arr, ...user.favoriteBooks.map(book => book.title)], []);

Welcome to the Treehouse Community

Looking to learn something new?

Jordan Mor

Jordan Mor

Is this a more effective solution to the second challenge in this lesson?

2 Answers

Steven Parker

Steven Parker

Jordan Mor

Jordan Mor

Brenden Seidel

Brenden Seidel