Group like JSON objects into arrays

Question

I have a model returned by a library in the following format:

var givenData = [{"fName": "john"}, {"fName": "mike"}, {"country": "USA"}]

How do I group the "fName" together and add '[]' to get:

{ 'fName[]': ['john','mike'],'country[]': ['USA'] };

**Note country and fName are not related at all.

you... loop over the array, and on each iteration, modify the output object based on the current array item... — user400654
– user400654, Commented Feb 6, 2017 at 21:52
It's getting downvoted because SO is not a code-writing service; please review How to ask a good question — Hamms
– Hamms, Commented Feb 6, 2017 at 21:59

luiscrjr · Accepted Answer · 2017-02-06 22:34:38Z

1

Suggestion (using ES6 syntax)

const transformData = (data) => {
  const newData = {}
  data.forEach( (item) => {
    for (let key in item) {
       const newKey = key + "[]"
       if (!newData.hasOwnProperty(newKey)) newData[newKey] = []
       newData[newKey].push(item[key])
    }
  })
  return newData
}

/* added some extra keys just to test */
let givenData = [
  {"fName": "john", "country": "England"}, 
  {"fName": "mike"}, 
  {"country": "USA"},
  {"language": "English"}
]

console.log(transformData(givenData))
/*
{
    "fName[]": ["john","mike"],
    "country[]": ["England","USA"],
    "language[]":["English"]
}
*/

edited Feb 6, 2017 at 22:34

answered Feb 6, 2017 at 22:00

luiscrjr

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Comments

Rodrigo5244 · Accepted Answer · 2017-02-06 21:55:03Z

1

You can iterate over the array and push the date to the desired field.

var givenData = [{"fName": "john"}, {"fName": "mike"}, {"country": "USA"}]

var result = {
  'fName[]': [],
  'country[]': []
};

givenData.forEach(function (data) {
  if (data.fName) {
    result['fName[]'].push(data.fName);
  }
  
  if (data.country) {
    result['country[]'].push(data.country);
  }
});

console.log(result);

answered Feb 6, 2017 at 21:55

Rodrigo5244

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Comments

Nina Scholz · Accepted Answer · 2017-02-06 21:58:37Z

1

You could take the key and build an object with the key and arrays as properties.

var givenData = [{"fName": "john"}, {"fName": "mike"}, {"country": "USA"}],
    grouped = givenData.reduce(function (r, o) {
        var key = Object.keys(o)[0] + '[]';
        r[key] = r[key] || [];
        r[key].push(o[Object.keys(o)[0]]);
        return r;
    }, Object.create(null));

console.log(grouped);

answered Feb 6, 2017 at 21:58

Nina Scholz

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2 Comments

Tolgahan Albayrak Over a year ago

Whoever downvoted this answer, should leave a comment for the reason

GavinBelson Over a year ago

Agreed, these are all good answers, someone downvoted all of them

mrBorna · Accepted Answer · 2017-02-06 22:55:06Z

0

In ES6:

const newData = givenData.reduce(function (r, o) { const key = `${Object.keys(o)[0]}[]`; return { ...r, [key]: [ ...r[key], o[key] ] } }, {});

This doesn't modify your original data and is very clean.

answered Feb 6, 2017 at 22:55

mrBorna

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