Modify properties of objects in array, based on string array

Question

First of all, I'm sorry that this might be a duplicate of another question somewhere, but I don't know if my wording was wrong in my searches, but I couldn't find an exact solution to the issue I'm having, so I do apologize in advance if this is a duplicate.

Now the issue.

I have an array of objects, that has various properties. I then have another array of strings, where each string represents the name of a property on the objects from the object array.

I want to create a new array of objects, but where the objects in the array, only have the properties with names from the string array.

I have been messing around with this one for a couple of hours, but haven't really got it to work as intended. I've tried doing some Object.keys stuff, combined with both map and indexOf, but I feel like I'm missing something in my logic, and at this point I'm just not sure what.

So basically I have an array of objects:

data = [
    {
        id: 1,
        name: 'john',
        value: 5
    },
    {
        id: 2,
        name: 'ben',
        value: 10
    },
    {
        id: 3,
        name: 'lisa',
        value: 12
    },
];

And an array of strings: desiredKeys = ['id', 'name'];

And I want to create a new array of objects, where each objects only has the 'id' and 'name' property.

Here's a plunker:

https://next.plnkr.co/edit/nU4Y85j7NFuFQqAx?open=lib%2Fapp.ts

My goal would be to create a new array of objects, but where the objects only have the properties in the 'desiredKeys'array, ie:

[
    {
        id: 1,
        name: 'john'
    },
    {
        id: 2,
        name: 'ben'
    },
    {
        id: 3,
        name: 'lisa'
    },
];

Any tips are welcome, thanks in advance!

adiga · Accepted Answer · 2019-08-01 07:37:43Z

3

You could map the data array and use Object.fromEntries() like this:

const data=[{id:1,name:"john",value:5},{id:2,name:"ben",value:10},{id:3,name:"lisa",value:12},],
      desiredKeys = ['id', 'name'];

const output = data.map(o => 
  Object.fromEntries( desiredKeys.map(k => [k, o[k]]))
)

console.log(output)

If Object.fromEntries() is not supported, you could reduce the keys to get a subset of each object:

const data=[{id:1,name:"john",value:5},{id:2,name:"ben",value:10},{id:3,name:"lisa",value:12},],
      desiredKeys = ['id', 'name'];

const output = data.map(o => 
 desiredKeys.reduce((a, k) => ({ ...a, [k]: o[k] }), {})
)

console.log(output)

answered Aug 1, 2019 at 7:37

adiga

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1 Comment

Jesper Over a year ago

Thanks for the tip! I chose your solution as the answer, as I found the reduce approach to be very elegant. Thanks again :)

brk · Accepted Answer · 2019-08-01 07:38:30Z

1

You can use map and forEach. Inside map call back iterate over the desiredKey and get the key and value from corresponding object

let data = [{
    id: 1,
    name: 'john',
    value: 5
  },
  {
    id: 2,
    name: 'ben',
    value: 10
  },
  {
    id: 3,
    name: 'lisa',
    value: 12
  },
];
let desiredKeys = ['id', 'name'];

let newData = data.map(function(item) {
  let newObj = {};
  desiredKeys.forEach(function(elem) {
    newObj[elem] = item[elem]
  })
  return newObj;

});

console.log(newData)

answered Aug 1, 2019 at 7:38

brk

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1 Comment

Jesper Over a year ago

Thanks for the tip! I was headed through something like this myself, allthough you cleared it up for me where I went wrong :) I chose the above answer, since I like the usage of reduce, but thanks for a good suggestion as well!

billyjov · Accepted Answer · 2019-08-01 07:37:50Z

0

Simple Way with less code

With Vanilla JavaScript you can just use the map operator like this:

const data = [
        {
            id: 1,
            name: 'john',
            value: 5
        },
        {
            id: 2,
            name: 'ben',
            value: 10
        },
        {
            id: 3,
            name: 'lisa',
            value: 12
        },
    ];
    
const newData = data.map(({id, name}) => ({ id, name }));

console.log(newData);

answered Aug 1, 2019 at 7:37

billyjov

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1 Comment

Jesper Over a year ago

Thanks for the tip! Unfortunately, your solution doesn't take in to consideration that the properties I want should be collected from a string array, but one of the above suggestions did so I picked that as a solution. Still thanks for your suggestion :)

Tuhin Das · Accepted Answer · 2019-08-01 07:44:53Z

0

First copy the data array. Use this it will just remove the value property from each element.

data.forEach((i)=>  delete i.value )

answered Aug 1, 2019 at 7:44

Tuhin Das

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