JavaScript: Add new attribute to object in an array

Question

I am trying to add an item into an existing object in an array (index each array):

const dataInput = [
  { title: 'first', description: 'test 1' },
  { title: 'second', description: 'test 1' },
]

This is what I've tried:

dataInput.map((data, index) => {
  availableItems.push({'idx':index})
})

This pushes a new object instead of adding the element to the existing first and second.

[
  { title: 'first', description: 'test 1' },
  { title: 'second', description: 'test 1' },
  {idx:0},
  {idx:1}
]

How could I achieve that? (below is what I need)

[
  { title: 'first', description: 'test 1', idx: 0 },
  { title: 'second', description: 'test 1', idx:1 },
]

Majed Badawi · Accepted Answer · 2020-12-27 12:42:16Z

6

You need to add a new attribute at each iteration:

const dataInput = [
  { title: 'first', description: 'test 1' },
  { title: 'second', description: 'test 1' },
];

const res = dataInput.map( (data, index) => ({...data, idx:index}) );

console.log(res);

edited Dec 27, 2020 at 12:42

answered Dec 27, 2020 at 12:35

Majed Badawi

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Comments

arielhad · Accepted Answer · 2020-12-27 12:42:02Z

2

Another option:

dataInput.forEach((element, index) => (element["idx"] = index));

answered Dec 27, 2020 at 12:42

arielhad

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Comments

Yves Kipondo · Accepted Answer · 2020-12-27 12:51:57Z

1

Another option:

const dataInput= [
  { title: 'first', description: 'test 1' },
  { title: 'second', description: 'test 1' },
]

const result = dataInput.reduce((acc, cur, index) => {
    acc.push({...cur, idx: index})
    return acc
},[])

console.log(result)

edited Dec 27, 2020 at 12:51

Yves Kipondo

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answered Dec 27, 2020 at 12:48

Punit Makwana

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