Using map function in Javascript to return new values

Question

This is my json:

[ { gsm: 'gsm',
  firstName: 'firstname',
  lastName: 'lastname' },
{ gsm: '123456789',
  firstName: 'Mohamed',
  lastName: 'Sameer'},
{ gsm: '987654321',
  firstName: 'Hameed',
  lastName: 'Basha'}]

I want my final output looks like:

[ { gsm: 'gsm',
  firstName: 'firstname',
  lastName: 'lastname',
  userKey: 'Key1'},
{ gsm: '123456789',
  firstName: 'Mohamed',
  lastName: 'Sameer',
  userKey: 'Key1'},
{ gsm: '987654321',
  firstName: 'Hameed',
  lastName: 'Basha',
  userKey: 'Key1'}]

i need to do this using any of the javascript methods like map...etc

Possible duplicate of Add property to an array of objects

Niklesh Raut
– Niklesh Raut

2018-01-11 07:16:24 +00:00
Commented Jan 11, 2018 at 7:16 — Niklesh Raut
– Niklesh Raut, Commented Jan 11, 2018 at 7:16

gurvinder372 · Accepted Answer · 2018-01-11 07:10:00Z

5

Use map

var output = arr.map( s => ( s.userKey = "Key1", s ) );

Demo

var arr = [{
    gsm: 'gsm',
    firstName: 'firstname',
    lastName: 'lastname'
  },
  {
    gsm: '123456789',
    firstName: 'Mohamed',
    lastName: 'Sameer'
  },
  {
    gsm: '987654321',
    firstName: 'Hameed',
    lastName: 'Basha'
  }
];

var output = arr.map( s => ( s.userKey = "Key1", s ) );

console.log( output );

answered Jan 11, 2018 at 7:10

gurvinder372

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3 Comments

Sebastian Simon Over a year ago

This will mutate the original array arr.

Paul Over a year ago

I think forEach is more appropriate in this case arr.forEach( s => s.userKey = "Key1" );. since none of the values in the array are updated, only the objects they reference are.

gurvinder372 Over a year ago

@Xufox If OP doesn't want the original array to be mutated, then Nina's answer is good enough. I was going to do the same thing but realized that Nina has done it already.

Nina Scholz · Accepted Answer · 2018-01-11 07:19:26Z

2

You could use Object.assign for generating a copy of the object and assign a new property and take Array#map for getting a new array.

var original = [ { gsm: 'gsm', firstName: 'firstname', lastName: 'lastname' }, { gsm: '123456789', firstName: 'Mohamed', lastName: 'Sameer' }, { gsm: '987654321', firstName: 'Hameed', lastName: 'Basha' }],
    copy = original.map(o => Object.assign({}, o, { key: 'key1' }));
    
console.log(copy);
console.log(original);

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

answered Jan 11, 2018 at 7:19

Nina Scholz

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Comments

Hemerson Carlin · Accepted Answer · 2018-01-11 07:17:11Z

1

In case you don't want to mutate the original array:

const arr = [ { gsm: 'gsm',
  firstName: 'firstname',
  lastName: 'lastname' },
{ gsm: '123456789',
  firstName: 'Mohamed',
  lastName: 'Sameer'},
{ gsm: '987654321',
  firstName: 'Hameed',
  lastName: 'Basha'}]
  
 const newArr = arr.map(item => ({
   ...item,
   userKey: 'Key1',
 }))
 
 console.log(newArr)

answered Jan 11, 2018 at 7:17

Hemerson Carlin

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Comments

Sameer · Accepted Answer · 2018-01-11 07:20:07Z

0

You can do like this :)

var data = [ { gsm: 'gsm',
  firstName: 'firstname',
  lastName: 'lastname' },
{ gsm: '123456789',
  firstName: 'Mohamed',
  lastName: 'Sameer'},
{ gsm: '987654321',
  firstName: 'Hameed',
  lastName: 'Basha'}]
  
 var finalarray = data.map(x => (x.userKey = 'Key1', x));
 console.log(finalarray);

answered Jan 11, 2018 at 7:20

Sameer

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1 Comment

user7784271 Over a year ago

he is putting with snippet

Pablo · Accepted Answer · 2018-01-11 07:16:03Z

0

data.map(el => Object.assign(el, {userKey: 'Key1'}))

or

data.map(el => ({ ...el, userKey: 'Key1' }))

answered Jan 11, 2018 at 7:16

Pablo

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1 Comment

iBug Over a year ago

Thank you for this code snippet, which might provide some limited, immediate help. A proper explanation would greatly improve its long-term value by showing why this is a good solution to the problem, and would make it more useful to future readers with other, similar questions. Please edit your answer to add some explanation, including the assumptions you've made.

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