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)
]

What's that output meant to be, an array of functions? Or did you mean [ 'Aditya(3)', 'Abhi(2)', 'goyal(1)']? — Andy
– Andy, Commented Nov 21, 2019 at 14:48

Ori Drori · Accepted Answer · 2019-11-21 19:55:06Z

4

You can use _.countBy() to get an object of names with count, or a _.groupBy() if you want an object of names with arrays.

An array of arrays using _.groupBy() and _.values():

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

const result = _.values(_.groupBy(names))

console.log(result)

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

And object of counts with _.countBy:

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

const result = _.countBy(names)

console.log(result)

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

Update - to get an array of strings that combine the key and value, you can use _.countBy(), and then _.map() it (lodash's _.map() works on objects as well).

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

const result = _.map(_.countBy(names), (v, k) => `${k}(${v})`)

console.log(result)

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

edited Nov 21, 2019 at 19:55

answered Nov 21, 2019 at 14:39

Ori Drori

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1 Comment

Aditya Over a year ago

Hey if you can answer this stackoverflow.com/questions/53856633/…

Andy · Accepted Answer · 2019-11-21 15:32:09Z

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);

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