How to edit object array?

Question

I want to edit JavaScript object.

I have an JavaScript object like this

data_without_id = [
                   0: {id: 1, name: "Mary", age: null}
                   1: {id: 2, name: "Bob", age: 33}
                   2: {id: 1, name: "Kelly", age: 40}
                  ]

I want to convert this object into this

data_without_id = [
                   0: {id: 1, name: "Kelly", age: 40}
                   1: {id: 2, name: "Bob", age: 33}
                  ]

What I need to do is:

Group by id
Get latest value.

I tried using Array.prototype.reduce(), but I can't get the result I need...

Ele · Accepted Answer · 2019-02-25 02:15:26Z

1

Using the function reduce would be as follow:

The function reduce for grouping and the function Object.values for extracting the values.

let data_without_id = [  {    id: 1,    name: "Mary",    age: null  },  {    id: 2,    name: "Bob",    age: 33  },  {    id: 1,    name: "Kelly",    age: 40  }],
    result = Object.values(data_without_id.reduce((a, {id, name, age}) => {
      a[id] = {id, name, age};
      return a;
    }, Object.create(null)));

console.log(result)

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

answered Feb 25, 2019 at 2:15

Ele

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1 Comment

Kiki Over a year ago

Thank you so much for super fast response! It works perfectly!

Nick Parsons · Accepted Answer · 2019-02-25 02:27:41Z

0

You could use .reduce by making the accumulator an object that has keys of the id. This way you can overwrite any previously seen objects which had the same id, and then use Object.values to get your array of objects:

const data_without_id = [{id: 1, name: "Mary", age: null}, {id: 2, name: "Bob", age: 33}, {id: 1, name: "Kelly", age: 40}],

res = Object.values(data_without_id.reduce((acc, obj) => 
  (acc[obj.id] = obj, acc)
, {}));
console.log(res);

edited Feb 25, 2019 at 2:27

answered Feb 25, 2019 at 2:15

Nick Parsons

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Comments

Andy · Accepted Answer · 2019-02-25 12:30:05Z

0

You could just simply use a for/of loop to create a copy of the data where the last object with a particular id will always be the object returned in the output data. This avoids the "grouping" part of the code but still returns the correct data.

const data_without_id = [
  { id: 1, name: "Mary", age: null },
  { id: 2, name: "Bob", age: 33 },
  { id: 1, name: "Kelly", age: 40 }
];

function lastId(arr) {
  const out = [];
  for (let obj of arr) {

    // If you don't create a copy of each object the returned
    // data will simply be contain _references_ to the original
    // data. Changes in the original data will be reflected
    // in the returned data
    out[obj.id - 1] = { ...obj };
  }
  return out;
}

const lastIds = lastId(data_without_id);
console.log(lastIds);

edited Feb 25, 2019 at 12:30

answered Feb 25, 2019 at 2:20

Andy

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