how to union/merge the array inside array in angular

Question

How to merge or union the array of array in angular

const b: any = [];
b.push(
  [
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-21 08:08:00" }
  ],
  [{ date: "2019-12-20 08:08:00" }, { date: "2019-10-20 08:08:00" }],
  [{ date: "2019-12-20 08:08:00" }, { date: "2019-12-30 08:08:00" }]
);
uniq(flatten(b, true), true, item => item.date); //error here

error:Expected 1 arguments, but got 3.

and remove the duplicate using the lodash uniqBy.

expected output:

[
    "2019-12-21 08:08:00",
    "2019-12-20 08:08:00",
    "2019-12-30 08:08:00"
]

Does this answer your question? [Merge/flatten an array of arrays](https://stackoverflow.com/questions/10865025/merge-flatten-an-array-of-arrays) — Armen Stepanyan, Jan 22 '20 at 06:49

Paritosh · Answer 1 · 2020-01-22T06:59:01.737

1

You can use Underscore - uniq and flatten to achieve this.

const b: any = []; b.push(   [
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-21 08:08:00" }   
   ],
   [
    { date: "2019-12-20 08:08:00" },
    { date: "2019-10-20 08:08:00" }
   ],
   [
    { date: "2019-12-20 08:08:00" }, 
    { date: "2019-12-30 08:08:00" }
   ] );
_.uniq(_.flatten(b, true), true, item => item.date)

Result:

[{date:"2019-12-20 08:08:00"},
{date:"2019-12-21 08:08:00"},
{date:"2019-10-20 08:08:00"},
{date:"2019-12-30 08:08:00"}]

With lodash, below is the way

_.uniqBy(_.flatten(b, item => item.date), 'date')

edited Jan 22 '20 at 06:59

answered Jan 22 '20 at 06:50

Paritosh

11,144
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can you show an out put – ABC Jan 22 '20 at 06:50
Copy this code, Go to https://underscorejs.org, F12, paste it to console and check – Paritosh Jan 22 '20 at 06:52
how to use it in lodash? – ABC Jan 22 '20 at 06:53
why not? I guess these functions should also work with it. – Paritosh Jan 22 '20 at 06:54
I'll try it on stackblitz – ABC Jan 22 '20 at 06:56
https://stackblitz.com/edit/angular-lodash-n9uuzq?file=app/app.component.ts – ABC Jan 22 '20 at 06:59
updated the answer for lodash – Paritosh Jan 22 '20 at 06:59
done update the answer for lodash – ABC Jan 22 '20 at 07:04
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/206415/discussion-between-abc-and-paritosh). – ABC Jan 22 '20 at 07:41
Parameter 'item' implicitly has an 'any' type, but when i'll add to ```_.uniqBy(_.flatten(b, (item: any) => item.date), 'date')``` Expected 1 arguments, but got 2 – ABC Jan 22 '20 at 07:44

score 1 · Answer 2 · answered Jan 22 '20 at 07:04

1

We can use vanilla JavaScript. So what we need is:

Map to get only unique items from array
flatMap method to flat array
Array.from to create array from Map collection

So code looks like this:

const result = new Map(b.flatMap(s => s).map(a => [a.date]));
let uniques = Array.from(result.keys());

An example:

const b = [];
b.push(
  [
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-20 08:08:00" },
    { date: "2019-12-21 08:08:00" }
  ],
  [
    { date: "2019-12-20 08:08:00" },
    { date: "2019-10-20 08:08:00" }
  ],
  [{ date: "2019-12-20 08:08:00" },
  { date: "2019-12-30 08:08:00" }]
);

const result = new Map(b.flatMap(s => s).map(a => [a.date]));
console.log(Array.from(result.keys()));

answered Jan 22 '20 at 07:04

StepUp

36,391
15
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https://stackblitz.com/edit/angular-lodash-n9uuzq?file=app/app.component.ts – ABC Jan 22 '20 at 07:09
@ABC yeah, it works. – StepUp Jan 22 '20 at 07:13
Property 'flatMap' does not exist on type 'any[]'. – ABC Jan 22 '20 at 07:14
not working.... – ABC Jan 22 '20 at 07:18
@ABC It looks like you need to set some settings into your configuration [Typescript flatMap, flat, flatten doesn't exist on type any](https://stackoverflow.com/questions/53556409/typescript-flatmap-flat-flatten-doesnt-exist-on-type-any) – StepUp Jan 22 '20 at 07:24

how to union/merge the array inside array in angular

2 Answers2