CODEWITHSUNDEEP
javascriptecmascript-6
Monski
Monski

Reputation: 310

Filter Array from array

I want to filter the objects from array:

let x = [{a: 100, categories: [22, 23 ] 

}, {a: 101, categories: [20, 21 ] }];
let y = [22]; //can be multiple

let result = x.filter(i => y.includes(i.categories)  );
console.log(result);
// result = []

Expected Output: 

[{a: 100, categories: [22, 23 ]}]

but I get empty array.

Upvotes: 0

Views: 63

Answers (3)

Mulan
Mulan

Reputation: 135227

If x, .categories, or y is significantly large, you can achieve a significant speed improvement by first converting y to a Set. Set.prototype.has provides much faster lookup times, O(1), compared to Array.prototype.includes, O(n) -

const x =
  [ { a: 100, categories: [ 22, 23 ] }
  , { a: 101, categories: [ 20, 21 ] }
  , { a: 102 }
  ]
  
const y =
  [ 22 ] //can be multiple

const ySet =
  new Set(y) // has O(1) lookup

let result =
  x.filter(({ categories = [] }) =>
    categories.some(c => ySet.has(c)) // <-- use set lookup
  )
  
console.log(result)
// [ { a: 100, categories: [ 22, 23 ] } ]

Upvotes: 0

Get Off My Lawn
Get Off My Lawn

Reputation: 36311

Use some to see if some of the items are in the categories array.

let x = [{a: 100, categories: [22, 23 ] }, {a: 101, categories: [20, 21 ] }];
let y = [22]; //can be multiple

let result = x.filter(i => y.some(a => i.categories.includes(a)));

console.log(result);

Upvotes: 2

Djaouad
Djaouad

Reputation: 22776

You're checking whether the entire array i.categories is in y, use Array.prototype.some to check if any element of i.categories is in y:

let x = [{a: 100, categories: [22, 23 ] }, {a: 101, categories: [20, 21 ] }];
let y = [22]; //can be multiple

let result = x.filter(i => y.some(x => i.categories.includes(x)));

console.log(result);

Upvotes: 1

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