How to get keys and count of each key from an array of objects

Question

I am trying to get the expected results below, but I am struggling. What is the best way to do it?

const data = [{
    name: 'Dave',
    country: 'England',
    color: 'Brown'
  },
  {
    name: 'Dave',
    country: 'England',
    color: 'white'
  },
  {
    name: 'Cae',
    country: 'USA',
    color: 'white'
  },
  {
    name: 'Dave',
    country: 'England',
    color: 'Red'
  },
  {
    name: 'Cae',
    country: 'USA',
    color: 'Yellow'
  },
  {
    name: 'Dave',
    country: 'England',
    color: 'white'
  },
  {
    name: 'Manuel',
    country: 'USA',
    color: 'Red'
  },
  {
    name: 'Dave',
    country: 'England',
    color: 'white'
  }
];


// Tentative:

(function getDataForName() {
  count = 0;
  nameL = [];
  nameCount = [];
  for (let i = 0; i < data.length; i++) {
    if (nameL.indexOf(data[i].name) === -1) {
      nameL.push(data[i].name);
      count++;
    }
    nameCount.push(count);
  }
  console.log(nameL);
  console.log(nameCount);
})()

Expected Results:

nameL = ['Dave', 'Cae', 'Manuel'];
nameCount = [4, 2, 1];

Is this a learning exercise or just need a snippet that works? chrisz answer works, but might be confusing to a learner — MindlessRouse
– MindlessRouse, Commented Mar 1, 2018 at 18:11
Remember to pick your answer carefully so others see your problem was solved. If you have any questions regarding any of the answers given, feel free to ask in the comments of that answer. — connexo
– connexo, Commented Mar 1, 2018 at 23:57

Nenad Vracar · Accepted Answer · 2018-03-01 18:11:26Z

2

With Lodash you can use countBy method to get one object and then you can use keys and values methods on that object.

const data = [{name: 'Dave', country: 'England', color: 'Brown'},{name: 'Dave', country: 'England', color: 'white'},{name: 'Cae', country: 'USA', color: 'white'},{name: 'Dave', country: 'England', color: 'Red'},{name: 'Cae', country: 'USA', color: 'Yellow'},{name: 'Dave', country: 'England', color: 'white'},{name: 'Manuel', country: 'USA', color: 'Red'},{name: 'Dave', country: 'England', color: 'white'}]

const result = _.countBy(data, 'name')
const names = _.keys(result);
const count = _.values(result);

console.log(names);
console.log(count)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

answered Mar 1, 2018 at 18:11

Nenad Vracar

122k16 gold badges160 silver badges184 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

connexo Over a year ago

You have an elegant solution using vanilla ES6?

Ele Over a year ago

@connexo that's not vallina JS ES6

user3483203 · Accepted Answer · 2018-03-01 18:16:12Z

2

How does this work for you? Array.prototype.reduce() just keeps calling this callback on the array while passing in the previous values.

const data = [{name: 'Dave', country: 'England', color: 'Brown'},{name: 'Dave', country: 'England', color: 'white'},{name: 'Cae', country: 'USA', color: 'white'},{name: 'Dave', country: 'England', color: 'Red'},{name: 'Cae', country: 'USA', color: 'Yellow'},{name: 'Dave', country: 'England', color: 'white'},{name: 'Manuel', country: 'USA', color: 'Red'},{name: 'Dave', country: 'England', color: 'white'}];

x = data.reduce(function(sums,entry){
   sums[entry.name] = (sums[entry.name] || 0) + 1;
   return sums;
},{});

console.log(x)

edited Mar 1, 2018 at 18:16

answered Mar 1, 2018 at 18:08

user3483203

51.3k10 gold badges72 silver badges104 bronze badges

Comments

stasovlas · Accepted Answer · 2018-03-01 20:31:42Z

1

another way:

const [nameL, nameCount] = _.chain(data)
    .groupBy('name')
    .mapValues(_.size)
    .toPairs()
    .thru(_.spread(_.zip))
    .value();

answered Mar 1, 2018 at 20:31

stasovlas

7,4362 gold badges30 silver badges30 bronze badges

1 Comment

ryeballar Over a year ago

You can replace the .groupBy() and .mapValues() pair with a single countBy('name') call. Additionally, you don't need to use the explicit chain method, _.chain(data), you can safely use the implicit chain method, _(data), in this case.

Ele · Accepted Answer · 2018-03-01 18:20:59Z

0

Use the function forEach along with functions Object.keys and Object.values.

const data = [    {name: 'Dave', country: 'England', color: 'Brown'},    {name: 'Dave', country: 'England', color: 'white'},    {name: 'Cae', country: 'USA', color: 'white'},    {name: 'Dave', country: 'England', color: 'Red'},    {name: 'Cae', country: 'USA', color: 'Yellow'},    {name: 'Dave', country: 'England', color: 'white'},    {name: 'Manuel', country: 'USA', color: 'Red'},    {name: 'Dave', country: 'England', color: 'white'}    ],
      a = {};

data.forEach((c) => a[c.name] = (a[c.name] || 0) + 1);

console.log(JSON.stringify(Object.keys(a)));
console.log(JSON.stringify(Object.values(a)));

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 1, 2018 at 18:20

answered Mar 1, 2018 at 18:15

Ele

33.8k7 gold badges43 silver badges80 bronze badges

Comments

connexo · Accepted Answer · 2018-03-01 19:48:22Z

0

This does it without any external libraries:

const data=[{name:'Dave',country:'England',color:'Brown'},{name:'Dave',country:'England',color:'white'},{name:'Cae',country:'USA',color:'white'},{name:'Dave',country:'England',color:'Red'},{name:'Cae',country:'USA',color:'Yellow'},{name:'Dave',country:'England',color:'white'},{name:'Manuel',country:'USA',color:'Red'},{name:'Dave',country:'England',color:'white'}];

const result = data.reduce(function(count, entry){
   count[entry.name] = count[entry.name] ? count[entry.name] + 1 : 1;
   return count;
},{});

console.log(Object.keys(result));
console.log(Object.values(result));

edited Mar 1, 2018 at 19:48

answered Mar 1, 2018 at 18:29

connexo

57.2k15 gold badges112 silver badges149 bronze badges

Collectives™ on Stack Overflow

How to get keys and count of each key from an array of objects

5 Answers 5

2 Comments

Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related