Create object while looping through an array

Question

I am trying to create an object using the values of items inside an array.

const arrOfObj = [
{city: 'Tokyo', country: 'Japan', ...other values},
{city: 'Paris', country: 'France', ...other values}, 
{city: 'London', country: 'UK', ...other values}, 
{city: 'New York', country: 'USA', ...other values}
]

expected object:

const obj = {
Japan: 'Tokyo', 
France: 'Paris', 
UK: 'London', 
USA: 'New York'
}

Can you guys have any suggestion to achieve this in an efficient way? All the comments will be highly appreciated. Thank you.

Possible duplicate of Reduce array to object using arrow function — eosterberg
– eosterberg, Commented Sep 8, 2019 at 19:17

Slai · Accepted Answer · 2019-09-08 19:27:35Z

2

Object.fromEntries can be used :

const arrOfObj = [
  { city: 'Tokyo'   , country: 'Japan'  },
  { city: 'Paris'   , country: 'France' }, 
  { city: 'London'  , country: 'UK'     }, 
  { city: 'New York', country: 'USA'    }
]

const obj = Object.fromEntries( arrOfObj.map(o => [o.country, o.city]) )

console.log( obj )

answered Sep 8, 2019 at 19:27

Slai

23k5 gold badges49 silver badges55 bronze badges

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

Comments

Addis · Accepted Answer · 2019-09-08 19:22:32Z

2

You can loop through the array and use the 'country' value as the property and set the value to the value of 'city'.

   const arrOfObj = [
    {city: 'Tokyo', countryL: 'Japan'},
    {city: 'Paris', countryL: 'France'}, 
    {city: 'London', countryL: 'UK'}, 
    {city: 'New York', countryL: 'USA'}
    ]

    let obj = {};
    arrOfObj.forEach(o => {obj[o.countryL] = o.city});

    console.log(JSON.stringify(obj))

answered Sep 8, 2019 at 19:22

Addis

2,5402 gold badges16 silver badges21 bronze badges

Comments

anthonygood · Accepted Answer · 2019-09-08 19:20:54Z

-2

Use Array.prototype.reduce:

arrOfObj.reduce((acc, { city, country }) => {
  acc[country] = city
  return acc
}, {})

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

edited Sep 8, 2019 at 19:20

answered Sep 8, 2019 at 19:17

anthonygood

4304 silver badges9 bronze badges

1 Comment

Joy Biswas Over a year ago

Try to explain your solution when you post an answer

Collectives™ on Stack Overflow

Create object while looping through an array

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related