How can I group by the array using lodash or javascript

Question

An Array is as follows:

let names = [
             'Aditya',
             'Aditya',
             'Aditya',
             'Abhi',
             'Abhi',
             'goyal'
            ]

I want to use lodash function and convert the names array which will return me as

[
  Aditya(3),
  Abhi(2),
  goyal(1)
]

Answer 1

1) _.countBy the names to produce an object with name/count as the key/value.

2) Use _.entries to convert the object to a set of nest entry arrays.

3) _.map over the entries to produce the required output.

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const toString = ([name, count]) => `${name}(${count})`;
const entries = _.entries(_.countBy(names));
const result = _.map(entries, toString);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

Alternatively you can use vanilla JS to achieve the same thing in (almost) the same amount of code using reduce, Object.entries, and map.

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const counts = names.reduce((acc, c) => {
  return acc[c] = (acc[c] || 0) + 1, acc;
}, {});

const toString = ([name, count]) => `${name}(${count})`;
const entries = Object.entries(counts);
const result2 = entries.map(toString);

console.log(result2);