Remove all duplicate occurrences of JSON object array

Question

originaData = [
{id: 1, description: abc },
{id: 2, description: def }
{id: 1, description: ghi }
{id: 3, description: jkl }
{id: 2, description: mno }
{id: 4, description: pqr }
]

expected result
uniqueData = [
{id: 3, description: jkl },
{id: 4, description: pqr }
]

duplicateData = [
{id: 1, description: abc },
{id: 2, description: def },
{id: 1, description: ghi },
{id: 2, description: mno }
]

I have already tried lodash's uniqBy. But It does not give me the expected results as it doesnt remove all the duplicate occurrences.

Kamesh · Accepted Answer · 2020-04-24 05:25:41Z

1

You can do this using filter and find in vanilla javascript:

originaData.filter((o, index) => originaData.find((_o, _index) => o.id === _o.id && index !== _index))

The above will give you the duplicate data in your array.

To get an array without duplicate data just use ! in the function logic:

originaData.filter((o, index) => !originaData.find((_o, _index) => o.id === _o.id && index !== _index))

edited Apr 24, 2020 at 5:25

answered Apr 13, 2020 at 12:02

Kamesh

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Nina Scholz · Accepted Answer · 2020-04-13 12:07:29Z

1

You could group by id and sort the grouped data by lengths of the array.

var data = [{ id: 1, description: 'abc' }, { id: 2, description: 'def' }, { id: 1, description: 'ghi' }, { id: 3, description: 'jkl' }, { id: 2, description: 'mno' }, { id: 4, description: 'pqr' }],
    [duplicate, unique] = Object
        .values(data.reduce((r, o) => ((r[o.id] = r[o.id] || []).push(o), r), {}))
        .reduce((r, a) => (r[+(a.length === 1)].push(...a), r), [[], []]);        

console.log(unique);
console.log(duplicate);

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

answered Apr 13, 2020 at 12:07

Nina Scholz

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Comments

cbass · Accepted Answer · 2020-04-13 12:16:56Z

You can achieve this in vanilla javascript by using the Array.reduce method. First group the data by id, then divide the groups into unique and duplicate arrays. If you a group has only one item, the item is unique, or if the group has more than one entry, the containing entries are duplicates.

const originialData = [
  {id: 1, description: 'abc' },
  {id: 2, description: 'def' },
  {id: 1, description: 'ghi' },
  {id: 3, description: 'jkl' },
  {id: 2, description: 'mno' },
  {id: 4, description: 'pqr' }
]

// Group data as an object by using the Array.reduce method.
const groupedById = originialData.reduce((groups, item) => {
  // if a group has not yet been created, default to empty array.
  if (!groups[item.id]) {
    groups[item.id] = [];
  }

  // push the entry into the group
  groups[item.id].push(item);

  return groups;
}, {});

// Get the group keys
const groupKeys = Object.keys(groupedById);

// Iterate the group keys, and divide into unique and duplicates array
const [unique, duplicates] = groupKeys.reduce(([uniq, dupl], id) => {
  // Get the current group
  const group = groupedById[id];

  // Select array depending on length
  if (group.length === 1) { // if length is 1, then the item is unique
    uniq = uniq.concat(group);
  } else { // else the containing items are duplicates.
    dupl = dupl.concat(group);
  }


  return [uniq, dupl];
}, [[], []])

console.log(unique)

Working example here: https://jsbin.com/sijidacile/edit?js,console

3limin4t0r · Accepted Answer · 2020-04-13 12:39:49Z

You could tally the ids in the array. Then partition your data based upon the id count.

function tally(iterable, fn = obj => obj) {
  const tally = new Map();
  for (const item of iterable) {
    const key = fn(item);
    if (!tally.has(key)) tally.set(key, 0);
    tally.set(key, tally.get(key) + 1);
  }
  return tally;
}

function partition(iterable, fn = obj => obj) {
  const truthy = [], falsy = [];
  for (const item of iterable) {
    (fn(item) ? truthy : falsy).push(item);
  }
  return [truthy, falsy];
}

const originaData = [{id:1,description:'abc'},{id:2,description:'def'},{id:1,description:'ghi'},{id:3,description:'jkl'},{id:2,description:'mno'},{id:4,description:'pqr'}];
const idCount = tally(originaData, obj => obj.id);
const [uniqueData, duplicateData] =
  partition(originaData, obj => idCount.get(obj.id) == 1);

console.log(uniqueData);
console.log(duplicateData);

If you only need one of the two (uniqueData or duplicateData), use filter instead.

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