how to change a element inside an array in javascript and store it in new array

Question

i'm new to javascript I have an array of objects like

arr=[{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}]

what if i want to increase the value of likes by 1 where id is 1 and store the resulting array in arr2 ???

arr2=[{id:1,likes:11},{id:3,likes:13},{id:3,likes:1}]

Please edit your question and add more details like what's problem stoping you? — habib
– habib, Commented Dec 3, 2019 at 6:50

Narendra Chouhan · Accepted Answer · 2019-12-03 08:50:15Z

1

You can Do like this

const arr = [{ id: 1, likes: 10 }, { id: 3, likes: 13 }, { id: 3, likes: 1 }]
const arr2 = []
let obj = {}
for (let i = 0; i < arr.length; i++) {
    if (arr[i]['id'] === 1)
        obj = { id: arr[i]['id'], likes: arr[i]['likes'] + 1 }
    else
        obj = arr[i]

    arr2.push(obj)
}
console.log("arr",arr) 
console.log("arr2",arr2)

edited Dec 3, 2019 at 8:50

answered Dec 3, 2019 at 6:50

Narendra Chouhan

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6 Comments

Narendra Chouhan Over a year ago

downvoters, please dare to comment, what's wrong so that i could know, I think my answer is right.

Juhil Somaiya Over a year ago

though I haven't downvoted your reply, your code looks clean to me but just a suggestion, store the result in new array as mentioned in question.!

Juhil Somaiya Over a year ago

one more thing, try to use ES6 standards, use const / let according to usage instead of traditional var

Juhil Somaiya Over a year ago

Happy to help you.! @Narendra

Alexey Lebedev Over a year ago

@NarendraChouhan your answer is wrong because it mutates the original array as well.

|

User863 · Accepted Answer · 2019-12-03 06:52:13Z

1

Using map()

const arr = [{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}]

const arr2 = arr.map(i => (i.id === 1 && (i.likes += 1), i))

console.log(arr2)

answered Dec 3, 2019 at 6:52

User863

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Comments

dmitrydwhite · Accepted Answer · 2019-12-03 06:57:41Z

1

const arr = [{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}];
const arr2 = arr.map(obj =>
  obj.id === 1 ?
    { id: obj.id, likes: obj.likes + 1 } :
    obj
);

or maybe you want the id to be dynamic?

const increment_likes = (id, old) => old.map(obj =>
  obj.id === id ?
    { id: obj.id, likes: obj.likes + 1 } :
    obj
);
const arr2 = increment_likes(1, arr);

answered Dec 3, 2019 at 6:57

dmitrydwhite

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Comments

Viswanath Polaki · Accepted Answer · 2019-12-03 06:58:55Z

1

You can do in this way.

arr=[{id:1,likes:10},{id:3,likes:13},{id:5,likes:1}]
function increase_id_likes_by_one(id){
    for(i=0;i<arr.length;i++){
    if (arr[i]['id'] == id) {
        arr[i]['likes'] += 1;
    }
  }
  console.log(arr);
}
increase_id_likes_by_one(1);
increase_id_likes_by_one(3);
increase_id_likes_by_one(5);
increase_id_likes_by_one(5);

The function increase_id_likes_by_one will take id as argument and print the new array ( after increasing the count ).

answered Dec 3, 2019 at 6:58

Viswanath Polaki

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Comments

Ankit Agarwal · Accepted Answer · 2019-12-03 07:02:13Z

1

You can use Array.map():

var arr=[{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}];

var id = 1

var res = arr.map((obj) => {
  obj.id === 1? obj.likes++: obj.likes;
  return obj;
});
console.log(res);

answered Dec 3, 2019 at 7:02

Ankit Agarwal

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Comments

StepUp · Accepted Answer · 2019-12-03 07:08:45Z

1

An inline version of map method:

var arr=[{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}];

var id = 1

var res = arr.map(({id, likes}) => ({  
  id,
  likes : (id === 1? ++likes : likes)
}));
console.log(res);

answered Dec 3, 2019 at 7:08

StepUp

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Comments

Mamun · Accepted Answer · 2019-12-03 07:12:21Z

1

You can try with JSON.stringify() and JSON.parse() with Array.prototype.map():

var arr=[{id:1,likes:10},{id:3,likes:13},{id:3,likes:1}];

var arr2 = JSON.parse(JSON.stringify(arr)).map(i => {
  if(i.id==1) i.likes += 1;
  return i;
});
console.log(arr); //original array without modification
console.log(arr2); //new array with modification

answered Dec 3, 2019 at 7:12

Mamun

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