Counting occurrence of values in an array of objects in another array of objects

I need to create a Graphql query that outputs data from two arrays of objects. The arrays are:

  const authors = [
    {
      name: 'Robert Martin',
      id: 'afa51ab0-344d-11e9-a414-719c6709cf3e',
      born: 1952
    },
    {
      name: 'Martin Fowler',
      id: 'afa5b6f0-344d-11e9-a414-719c6709cf3e',
      born: 1963
    },
    {
      name: 'Fyodor Dostoevsky',
      id: 'afa5b6f1-344d-11e9-a414-719c6709cf3e',
      born: 1821
    },
    {
      name: 'Joshua Kerievsky', // birthyear not known
      id: 'afa5b6f2-344d-11e9-a414-719c6709cf3e'
    },
    {
      name: 'Sandi Metz', // birthyear not known
      id: 'afa5b6f3-344d-11e9-a414-719c6709cf3e'
    }
  ];

And:

  const books = [
    {
      title: 'Clean Code',
      published: 2008,
      author: 'Robert Martin',
      id: 'afa5b6f4-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring']
    },
    {
      title: 'Agile software development',
      published: 2002,
      author: 'Robert Martin',
      id: 'afa5b6f5-344d-11e9-a414-719c6709cf3e',
      genres: ['agile', 'patterns', 'design']
    },
    {
      title: 'Refactoring, edition 2',
      published: 2018,
      author: 'Martin Fowler',
      id: 'afa5de00-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring']
    },
    {
      title: 'Refactoring, edition 3',
      published: 2018,
      author: 'Martin Fowler',
      id: 'afa5de00-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring']
    },
    {
      title: 'Refactoring, edition 4',
      published: 2018,
      author: 'Martin Cowler',
      id: 'afa5de00-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring']
    },
    {
      title: 'Refactoring to patterns',
      published: 2008,
      author: 'Joshua Kerievsky',
      id: 'afa5de01-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring', 'patterns']
    },
    {
      title: 'Practical Object-Oriented Design, An Agile Primer Using 
       Ruby',
      published: 2012,
      author: 'Sandi Metz',
      id: 'afa5de02-344d-11e9-a414-719c6709cf3e',
      genres: ['refactoring', 'design']
    },
    {
      title: 'Crime and punishment',
      published: 1866,
      author: 'Fyodor Dostoevsky',
      id: 'afa5de03-344d-11e9-a414-719c6709cf3e',
      genres: ['classic', 'crime']
    },
    {
      title: 'The Demon ',
      published: 1872,
      author: 'Fyodor Dostoevsky',
      id: 'afa5de04-344d-11e9-a414-719c6709cf3e',
      genres: ['classic', 'revolution']
    }
  ];

The desired output format for a query like this:

query {
  allAuthors {
  name
  bookCount
 }

}

is like so:

    "data": {
      "allAuthors": [
        {
          "name": "Robert Martin",
          "bookCount": 2
        },
        {
          "name": "Martin Fowler",
          "bookCount": 1
        },
        {
          "name": "Fyodor Dostoevsky",
          "bookCount": 2
        },
        {
          "name": "Joshua Kerievsky",
          "bookCount": 1
        },
        {
          "name": "Sandi Metz",
          "bookCount": 1
        }
      ]
    }

I've found a way to count the amount of books for each author and output the data in the desired format (a good example of that here: Summarize count of occurrences in an array of objects with Array#reduce). However this approach ignores other fields in the data, such as "born" and "genres". If I was to expand the query like so:

    query {
     allAuthors {
      name
      bookCount
      born
     }
   }

It wouldn't output anything for the field "born". What would be the smart way to create the query resolver? Spread operator? Reduce?

* EDIT * My unnecessarily complicated solution for counting the books here:

 const newBooks = books.reduce((acc, cv) => {
    const arr = acc.filter(obj => {
      return obj.author === cv.author;
    });

    if (arr.length === 0) {
      acc.push({ name: cv.author, born: cv.born, bookCount: 1 });
    } else {
      arr[0].bookCount += 1;
    }

    return acc;
  }, []);
  const array = [];
  books.forEach(book => {
    const object = {
      name: book.author
    };
    array.push(object);
    return array;
  });
  const unique = array.map(a => a.name);
  result = {};
  for (var i = 0; i < unique.length; ++i) {
    if (!result[unique[i]]) result[unique[i]] = 0;
    ++result[unique[i]];
  }
  const entries = Object.entries(result);
  const finalAnswer = [];
  entries.forEach(entry => {
    const object = {
      name: entry[0],
      bookCount: entry[1]
    };
    finalAnswer.push(object);
    return finalAnswer;
  });
  console.log(finalAnswer);