remove object from array if property value match

Question

I have array of objects that look like:

{
  "brandid": id,
  "brand": string,
  "id": id,
  "categoryId": id,
  "category": string,
  "factory": string,
  "series": string,
  "status": 0,
  "subStatus": 1
}

if the series property value matches another series property value in the other objects in the array, that object needs to be removed from the array.

Currently I have attempted to push them to a duplicate Array with :

      const seriesResCopy = seriesRes;
      const dupArray = []
      for (const thing of seriesResCopy) {
        for (const item of seriesRes) {
          if (thing.series === item.series) {
            dupArray.push(item);
          }
        }
      }

but this does not work. From examples I have seem my issue has been that I do not have a definite list of duplicate values to look for.

Any help would be much appreciated.

push() doesn't remove an element from an array, it just puts a reference (or copy if primitive) into the other array. — Patrick Evans
– Patrick Evans, Commented Jun 8, 2018 at 18:08
You dont actually remove anything. That can be done with .splice — Jonas Wilms
– Jonas Wilms, Commented Jun 8, 2018 at 18:09
So you want to filter out duplicates, triplicates, etc? Only keeping the first instance? — tymeJV
– tymeJV, Commented Jun 8, 2018 at 18:10
I am wanting to filter duplicates and keep the first instance. — Brian Stanley
– Brian Stanley, Commented Jun 8, 2018 at 18:11
@mplungjan "an array of objects like" is not "i have an object like". Don't change the question! — Jonas Wilms
– Jonas Wilms, Commented Jun 9, 2018 at 9:14

Jonas Wilms · Accepted Answer · 2018-06-08 18:14:03Z

4

You could use a Set of series to filter out duplicates:

const exists = new Set();
seriesRes = seriesRes.filter(({series}) => !exists.has(series) && exists.add(series));

This uses: Array.prototype.filter, Object destructuring and some logical tricks.

The same can be done by mutating the array:

const exists = new Set();
for(const [index, {series}] of seriesRes.entries()) {
  if(!exists.has(series) {
    exists.add(series);
  } else {
    seriesRes.splice(index, 1);
  }
}

edited Jun 8, 2018 at 18:14

answered Jun 8, 2018 at 18:11

Jonas Wilms

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6 Comments

mplungjan Over a year ago

Please do explode the code and comment what it does. It is very elegant but very new (as of June 2018) too

Nina Scholz Over a year ago

fantastic idea with set, i have used it lately, or later or so.

Jonas Wilms Over a year ago

@mplungjan if you change the question, why should the answers still fit?!?

Jonas Wilms Over a year ago

@mplungjan the OP has accepted this answer. So if you say "this does not work for my weird snippet i made out of the OPs code" then this is a fault on your side, not my's.

mplungjan Over a year ago

It would not be the first time an asker posted an object and called it an array. So all I had to do was to wrap in []. That would have been useful if OP had shown a valid array in my opinion. So not so weird. Anyway your code is still interesting

|

tymeJV · Accepted Answer · 2018-06-08 18:12:56Z

0

To filter duplicates from the array and keep the first instance:

let seriesWithoutDuplicates = seriesRes.filter((s, i, self) => {
    return self.findIndex(z => z.series === s.series) === i;
});

answered Jun 8, 2018 at 18:12

tymeJV

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