How to find array in array

Question

I need to find the elements in a first array that match with elements in a second array. For example:

this.languages = [
      {id: 'es', name: 'Español'},
      {id: 'fr', name: 'Frances'},
      {id: 'en', name: 'Ingles'},
      {id: 'pt', name: 'Portugues'}
];

Must return the languages that match win the next array:

this.languagesSelected = [
      'es', 'fr'
];

The result will be:

this.languages = [
      {id: 'es', name: 'Español'},
      {id: 'fr', name: 'Frances'}
];

Tryng from :

questions.filter(x => x.id === id);
questions.find(x => x.id === id);

I cant compare the second array.

Thanks mates

Nick Parsons · Accepted Answer · 2021-01-14 10:24:28Z

2

This can be done efficiently by creating a Map of id: object pairs from your languages array, which you can use while you .map() over your languagesSelected array:

const languages = [ {id: 'es', name: 'Español'}, {id: 'fr', name: 'Frances'}, {id: 'en', name: 'Ingles'}, {id: 'pt', name: 'Portugues'} ];
const languagesSelected = ['es', 'fr'];

const lut = new Map(languages.map((o) => [o.id, o]));
const res = languagesSelected.map(k => lut.get(k));
console.log(res);

This will be O(N + K) vs the O(NK) you would get with a filter/includes/indexOf/some methods

answered Jan 14, 2021 at 10:24

Nick Parsons

51.6k6 gold badges61 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sara · Accepted Answer · 2021-01-14 10:26:41Z

You have a good start using filter() method, but your condition is not good. You need to check if any of the languages in selectedLanguages array exists in languages list. So here some() method will help.

The some() method tests whether at least one element in the array passes the test

let languages = [
      {id: 'es', name: 'Español'},
      {id: 'fr', name: 'Frances'},
      {id: 'en', name: 'Ingles'},
      {id: 'pt', name: 'Portugues'}
];

let languagesSelected = [
      'es', 'fr'
];

let result = languages.filter(e => languagesSelected.some(element => e.id == element));

console.log(result);

Another method you can use is includes()

The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.

let languages = [
      {id: 'es', name: 'Español'},
      {id: 'fr', name: 'Frances'},
      {id: 'en', name: 'Ingles'},
      {id: 'pt', name: 'Portugues'}
];

let languagesSelected = [
      'es', 'fr'
];

let result = languages.filter(e => languagesSelected.includes(e.id));;

console.log(result);

Lotte Lemmens · Accepted Answer · 2021-01-14 10:20:38Z

1

languages.filter(l=>this.languagesSelected.indexOf(l.id)>-1);

answered Jan 14, 2021 at 10:20

Lotte Lemmens

5815 silver badges11 bronze badges

Comments

Chrillewoodz · Accepted Answer · 2021-01-14 10:24:13Z

1

Try this:

const result = this.languages.filter(lang => this.languagesSelected.includes(lang.id));

edited Jan 14, 2021 at 10:24

answered Jan 14, 2021 at 10:20

Chrillewoodz

28.4k23 gold badges102 silver badges189 bronze badges

Collectives™ on Stack Overflow

How to find array in array

4 Answers 4

Comments

Comments

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Linked

Related