Javascript - Get a corresponding object between two arrays

Question

I have the following arrays:

First array:

const dummyJSON = [
    {
      id: 1,
      sponsor_date: '2020-08-16T22:45:03.154Z'
    },
    {
      id: 2,
      sponsor_date: '2020-09-16T22:45:03.154Z'
    },
    {
      id: 3,
      sponsor_date: '2020-09-01T22:45:03.154Z'
    }
  ]

Second array:

const validated = [ true, false, false ]

And I wanted to get the object (dummyJSON.id) when the corresponding (validated) array item is true.

Basically, if the first item in the validate [0] array has a value of "true", then I would like to have the corresponding [0] item's id value in the dummyJSON array.

Are you looking for all of the objects that have a true validated value? What's the desired output (an array of ID's? one ID?) — CollinD
– CollinD, Commented Sep 17, 2020 at 18:54

kind user · Accepted Answer · 2020-09-17 19:01:51Z

2

You can use Array#reduce to get array of validated ids.

It will basically loop over every element and if the index of currently iterated object corresponds to the truthy value inside validated with the very same index, the object's id will be pushed to the result.

const dummyJSON = [
    { id: 1, sponsor_date: '2020-08-16T22:45:03.154Z' },
    { id: 2, sponsor_date: '2020-09-16T22:45:03.154Z' },
    { id: 3, sponsor_date: '2020-09-01T22:45:03.154Z' }
];

const validated = [true, false, false];

const validatedIds = dummyJSON
  .reduce((s, { id }, i) => (validated[i] ? s.push(id) : s, s), []);

console.log(validatedIds);

edited Sep 17, 2020 at 19:01

answered Sep 17, 2020 at 18:56

kind user

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2 Comments

CollinD Over a year ago

Great solution, might be worth adding a bit of explanation, the reduce function can be a bit confusing if you've never used it before, especially combined with arg destructuring, one-letter variable names and a ternary lol

kind user Over a year ago

@CollinD Thank you, updated the answer with some details.

ray · Accepted Answer · 2020-09-17 19:07:49Z

2

If your goal is just to get the validated items, use filter:

const valid = dummyJSON.filter((item, index) => validated[index]);

If you just want the ids, add a map call:

const valid = dummyJSON.filter((item, index) => validated[index]);
const ids = valid.map(x => x.id);

This could be done in a single line if you prefer, by chaining the map call:

const ids = dummyJSON.filter((item, index) => validated[index]).map(x => x.id);

const dummyJSON = [
    { id: 1, sponsor_date: '2020-08-16T22:45:03.154Z' },
    { id: 2, sponsor_date: '2020-09-16T22:45:03.154Z' },
    { id: 3, sponsor_date: '2020-09-01T22:45:03.154Z' }
];

const validated = [ true, false, false ];

// source objects
console.log(dummyJSON.filter((_, index) => validated[index]));

// just the ids
console.log(dummyJSON.filter((_, index) => validated[index]).map(x => x.id));

edited Sep 17, 2020 at 19:07

answered Sep 17, 2020 at 18:57

ray

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2 Comments

kind user Over a year ago

I believe the asker wants only ids to be returned, not whole objects.

ray Over a year ago

Noted. Updated to add a map call to get the ids.

Goran.it · Accepted Answer · 2020-09-17 19:00:35Z

0

No need for reduce, filter can do that just as well and faster :

const validated = [ true, false, false ]
const dummyJSON = [
    {
      id: 1,
      sponsor_date: '2020-08-16T22:45:03.154Z'
    },
    {
      id: 2,
      sponsor_date: '2020-09-16T22:45:03.154Z'
    },
    {
      id: 3,
      sponsor_date: '2020-09-01T22:45:03.154Z'
    }
  ]
// To get all validated objects from dummy JSON
const validatedJSON = dummyJSON.filter((obj, index) => validated[index])
// To extract just the ID's
const validatedJSONIds = validatedJSON.map(json => json.id)

answered Sep 17, 2020 at 19:00

Goran.it

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