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How to remove duplicates from array if value set for one of the duplicates, else hold null (javascript/typescript)

December 29, 2022

I need to remove duplicate or empty values (sets) from an array in javascript (typescript) if there is data with a non-empty value on the exact same date. If all the values (sets) were empty on that day, we should keep one value.

Example:

0: (2) ['2022-12-05', null]   ---> Remove due to "Reason 1"
1: (2) ['2022-12-05', 2695.923015841]   ---> Remain because it has a y value (on 5 Dec)
2: (2) ['2022-12-05', null]   ---> Remove due to "Reason 1"
3: (2) ['2022-12-05', null]   ---> Remove due to "Reason 1"

4: (2) ['2022-12-12', null]   ---> Remove due to "Reason 1"
5: (2) ['2022-12-12', 3984.864626441]   ---> Remain because it has a y value (on 12 Dec)
6: (2) ['2022-12-12', null]   ---> Remove due to "Reason 1"
7: (2) ['2022-12-12', null]   ---> Remove due to "Reason 1"

8: (2) ['2022-12-19', null]   ---> Remove due to "Reason 2"
9: (2) ['2022-12-19', null]   ---> Remove due to "Reason 2"
10: (2) ['2022-12-19', null]   ---> Remove due to "Reason 2"
11: (2) ['2022-12-19', null]   ---> Remain because no y value on this date

Reason 1: This member of the array should be removed because we have a null value on the same date (as specified in the x).

0: (2) [x: Date, y: value]

Reason 2: This member should be removed because we have 4 duplicate objects with the same values we only need 1 of them.

Expected result:

It would be an array with 3 values (sets).

0: (2) ['2022-12-05', 2695.923015841]   ---> Remain because it has a y value 
1: (2) ['2022-12-12', 3984.864626441]   ---> Remain because it has a y value 
2: (2) ['2022-12-19', null]   ---> Remain because no y value on this date

>Solution :

const arr = [
  ['2022-12-05', null],
  ['2022-12-05', 2695.923015841],
  ['2022-12-05', null],
  ['2022-12-05', null],
  ['2022-12-12', null],
  ['2022-12-12', 3984.864626441],
  ['2022-12-12', null],
  ['2022-12-12', null],
  ['2022-12-19', null],
  ['2022-12-19', null],
  ['2022-12-19', null],
  ['2022-12-19', null],
];

const newArr = [...new Set(arr.map(item => item[0]))].map(item => {
  const findVal = arr.find(_item => _item[0] === item && _item[1]);
  if (findVal) return findVal;
  return [item, null];
});

console.log(newArr);