How to count values in a nested array using Lodash?

Question

I am trying to calculate the unique count of users.hobbies using Lodash. The data looks like this:

var users = [
  { 'user': 'barney', 'age': 36, 'hobbies': ['soccer','basketball']  },
  { 'user': 'fred',   'age': 40, 'hobbies': ['soccer', 'golf'] },
  { 'user': 'tom',   'age': 25,  'hobbies': ['golf'] }
];

I have tried:

_.countBy(users, 'hobbies');
// { 'soccer,basketball': 1, 'soccer,golf': 1, golf: 1 }

The desired output is:

// { 'soccer':2, 'basketball':1, 'golf':2}

I guess I would need to split the value of users.hobbies but I am not exactly sure how to apply it.

Answer 1

You can flatten the hobbies before:

const users = [
  { 'user': 'barney', 'age': 36, 'hobbies': ['soccer','basketball']  },
  { 'user': 'fred',   'age': 40, 'hobbies': ['soccer', 'golf'] },
  { 'user': 'tom',   'age': 25,  'hobbies': ['golf'] }
];

const count = _.countBy(users.flatMap(user => user.hobbies));
console.log(count);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>