lodash count unique of field

Question

I have an array of 500 objects each object looks like this:

{name: 'Hello', phone_num: '1234'}

Now i wish to find out how many there is of each name. So i wish to convert my array into the following:

[{name: 'Hello', count:15}, {name:'Marc', count:5}]

So i wish thinking of using lodash for this but looking at their documentation i haven't been able to find an answer.

They have something called countBy but it doesnt seem to be sufficient for this issue.

Can anyone help me out?

Answer 1

You can make use of groupBy() to group them by name and then map() each grouped items to return the necessary count and names.

var result = _(data)
  .groupBy('name')
  .map((items, name) => ({ name, count: items.length }))
  .value();

var data = [
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  { name: 'Hello', phone_num: '1234'},
  
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  { name: 'Marc', phone_num: '5432'},
  
  { name: 'Sam', phone_num: '76532'},
  { name: 'Sam', phone_num: '76532'},
  { name: 'Sam', phone_num: '76532'},
  { name: 'Sam', phone_num: '76532'}
  
];
  
var result = _(data)
  .groupBy('name')
  .map((items, name) => ({ name, count: items.length }))
  .value();
  
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.12.0/lodash.js"></script>

UPDATE:

The ES5 Version would be:

var result = _(data)
  .groupBy('name')
  .map(function(items, name) { 
     return { name: name, count: items.length };
  }).value();

Answer 2

My version:

var result = _(data)
  .countBy('name')
  .map((count, name) => ({ name, count }))
  .value();