Filter/select a javascript Objects by an Array content

Question

I am trying to filter these Javascript objects:

   A= [{
      asset_bubble: 17,
      biodiversity_loss: 15,
      code: "CH",
      critical_information: 14,
      cyber_attacks: 19,
      data_fraud: 13,
      deflation: 4,
      energy: 18,
      extreme_weather: 12,
      change_adaptation: 9,
      infrastructure: 33
   },
   {
     asset_bubble: 4,
     biodiversity_loss: 7,
     code: "TZ"
     critical_information: 9,
     cyber_attacks: 9,
     data_fraud: 10,
     deflation: 3,
     energy: 1,
     extreme_weather: 2,
     change_adaptation: 7
     infrastructure: 3
}]

By this array:

array=["data_fraud","change_adaptation", "deflation","code"]

The result I am looking for is:

B= [{     code: "CH",
          data_fraud: 13,
          deflation: 4,
          change_adaptation: 9
       },
       {
         code: "TZ"
         data_fraud: 10,
         deflation: 3,
         change_adaptation: 7
    }]

I have done this:

B = A.map(({ ...array }) => ({ ...array }))

But this is not working. I know map should do the work but how can I list the fields of the objects I want to filter out?

@evolutionxbox, yes whatever works. Though I thought map would be best — road
– road, Commented Oct 12, 2020 at 19:23
Map doesn't filter though. That's what filter does. --- Sorry I think I misread. You want to keep the same array size, but remove properties from each item object? — evolutionxbox
– evolutionxbox, Commented Oct 12, 2020 at 19:24
Actually you do want map here, because you want an array of the same length with transformed objects. — Robin Zigmond
– Robin Zigmond, Commented Oct 12, 2020 at 19:25

Derek Wang · Accepted Answer · 2020-10-12 19:25:37Z

5

Inside Array.map callback, you can map array variable values to [key, item[key]] pair and from that 2d array, you can generate the object using Object.fromEntries as follows.

const A = [{
  asset_bubble: 17,
  biodiversity_loss: 15,
  code: "CH",
  critical_information: 14,
  cyber_attacks: 19,
  data_fraud: 13,
  deflation: 4,
  energy: 18,
  extreme_weather: 12,
  change_adaptation: 9,
  infrastructure: 33
}, {
  asset_bubble: 4,
  biodiversity_loss: 7,
  code: "TZ",
  critical_information: 9,
  cyber_attacks: 9,
  data_fraud: 10,
  deflation: 3,
  energy: 1,
  extreme_weather: 2,
  change_adaptation: 7,
  infrastructure: 3
}];

const array = ["data_fraud","change_adaptation", "deflation","code"];

const B = A.map((item) => (
  Object.fromEntries(array.map((key) => ([key, item[key]])))
));
console.log(B);

answered Oct 12, 2020 at 19:25

Derek Wang

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Robin Zigmond · Accepted Answer · 2020-10-12 19:30:43Z

Here's another approach, using reduce:

const A= [ {
      asset_bubble: 17,
      biodiversity_loss: 15,
      code: "CH",
      critical_information: 14,
      cyber_attacks: 19,
      data_fraud: 13,
      deflation: 4,
      energy: 18,
      extreme_weather: 12,
      change_adaptation: 9,
      infrastructure: 33
   },
   {
     asset_bubble: 4,
     biodiversity_loss: 7,
     code: "TZ",
     critical_information: 9,
     cyber_attacks: 9,
     data_fraud: 10,
     deflation: 3,
     energy: 1,
     extreme_weather: 2,
     change_adaptation: 7,
     infrastructure: 3
}];

const array=["data_fraud","change_adaptation", "deflation","code"];

const B = A.map(item => array.reduce((acc, key) => ({ ...acc, [key]: item[key]}), {}));

console.log(B);

Thunderbolt Engineer · Accepted Answer · 2020-10-12 19:27:19Z

1

B = A.map(({ code, data_fraud, deflation, change_adaptation }) => ({ code, data_fraud, deflation, change_adaptation }))

I think this should work?

answered Oct 12, 2020 at 19:27

Thunderbolt Engineer

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1 Comment

Robin Zigmond Over a year ago

yes it does, but only because you've hard-coded the fields to keep. This won't work if array can be dynamic.

Mechanic · Accepted Answer · 2020-10-12 19:46:50Z

0

based on Derek's answer I made handy function to filter object by its keys:

function filterBykeys ( target, keyList ) {
  return Object.fromEntries(
    Object.entries(target).filter(
      ([key,value]) => keyList.includes(key)
    )
  )
}

and here is a snippet using this function

function filterBykeys ( target, keyList ) {
  return Object.fromEntries(
    Object.entries(target).filter(
      ([key,value]) => keyList.includes(key)
    )
  )
}

const data= [{
      asset_bubble: 17,
      biodiversity_loss: 15,
      code: "CH",
      critical_information: 14,
      cyber_attacks: 19,
      data_fraud: 13,
      deflation: 4,
      energy: 18,
      extreme_weather: 12,
      change_adaptation: 9,
      infrastructure: 33
   },
   {
     asset_bubble: 4,
     biodiversity_loss: 7,
     code: "TZ",
     critical_information: 9,
     cyber_attacks: 9,
     data_fraud: 10,
     deflation: 3,
     energy: 1,
     extreme_weather: 2,
     change_adaptation: 7,
     infrastructure: 3
}];

const arrays=["data_fraud","change_adaptation", "deflation","code"];

const result = data.map( obj => {
  return filterBykeys(obj, arrays);
});

console.log(result)

edited Oct 12, 2020 at 19:46

answered Oct 12, 2020 at 19:26

Mechanic

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1 Comment

Emiel Zuurbier Over a year ago

This only returns the keys.

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