CODEWITHSUNDEEP
reactjstypescriptreact-hookstsx
lo7
lo7

Reputation: 445

How to add a new value to existing object in array

How can I add a value to an object in the array persons?

The value I want to add is lastname and variable id is the id of the object the value should be added to.

const lastname = 'Jackson';
const id = 2;

const persons = [
    {
        id: 1
        firstname: 'Mary',
        lastname: 'Jackson'
    },

    {
        id: 2
        firstname: 'Ash'
    }
]

Upvotes: 0

Views: 134

Answers (3)

edbentley
edbentley

Reputation: 331

Here's a one-liner to update it without mutating the original array:

const updatedPersons = persons.map(p => p.id === id ? {...p, lastname} : p);

Upvotes: 2

rzwnahmd
rzwnahmd

Reputation: 1082

You need to loop over the array and add a condition to check if id matches person.id then add lastname to that person object. If you don't want to change the original array go for .map() else .forEach() With .forEach():

persons.forEach(person => {
  if (person.id === id) {
    person.lastname = lastname
  }
})

With .map():

const newPersonsArr = persons.map(person => {
  if (person.id === id) {
    return {
      ...person,
      lastname
    }
  }
  return person;
})

Upvotes: 1

user13258211
user13258211

Reputation: 

persons.forEach(person => {
    if(this.id === person.id) person.lastname = this.lastname
})

Upvotes: 1

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