Add Extra Key value on existing object under loop

Question

I have a data set like this:

[
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
]

Now For getting the value one by one I have created a loop. Under loop I am getting the value.

Now if I want to add extra key value on that object then how it will be done.?

I tried data[i].extrakey = "value"; console.log(data); but it will not set.

Any help is really appreciated

gurvinder372 · Accepted Answer · 2018-03-14 06:42:20Z

3

Use map

array = array.map( s => Object.assign( s, {extrakey : "value" } ) );

answered Mar 14, 2018 at 6:42

gurvinder372

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Comments

Faly · Accepted Answer · 2018-03-14 06:47:06Z

0

You can use spread along with array.prototype.map to add the extra key:

var arr = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
];

var result = arr.map(e => ({...e, extraKey: 'value'}));

console.log(result);

answered Mar 14, 2018 at 6:47

Faly

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Comments

Suren Srapyan · Accepted Answer · 2018-03-14 06:48:36Z

You can see it in the example below. Just iterating over the array and adding a new key will alter the objects inside the array, because object is a reference type and you are just working with a reference which changes the original object.

const array = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        }
];

array.forEach(item => item.extraKey = 'value');

console.log(array);

Also if you want to change the array items, it will be better to not change the original objects, but create their copies and provide a new array.

const array = [
        {
            "_id": "5aa7b6add9655d0bd4ce1f53",
            "user_name": "as",
            "createdate": "2018-03-13T11:31:57.133Z",
        },
        {
            "_id": "5aa7b6add9655d0bd4ce1f54",
            "user_name": "ds",
            "createdate": "2018-03-13T11:31:57.133Z",
        }
];

const newArray = array.map(item => Object.assign({}, item, { extraKey: 'value' }));

console.log(newArray);

Talib Allauddin · Accepted Answer · 2018-03-14 06:50:05Z

0

var array = [
    {
        "_id": "5aa7b6add9655d0bd4ce1f53",
        "user_name": "as",
        "createdate": "2018-03-13T11:31:57.133Z",
    },
    {
        "_id": "5aa7b6add9655d0bd4ce1f54",
        "user_name": "ds",
        "createdate": "2018-03-13T11:31:57.133Z",
    }
];
array = array.map( s => Object.assign( s, {extrakey : "value" } ) );

answered Mar 14, 2018 at 6:50

Talib Allauddin

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