Filter id in an array of object based on an array of id's

Question

I am trying to display Heart icon for the items that are added to the Wishlist. I am using local storage to save the items that are wishlisted. I have an array of id's such as wishlistIds = [123,425,212,512,516]. So I want to check if the id's in that array matches with the array of objects (which are the products). Product array of objects looks like this;

 items = [{id:123, productName:"Cheese", price: 15.99}, {id:599, productName: "Honey", price:21.99}]

I have been trying to use Array.filter method to achieve what I want, but couldn't make it work;

wishlistIds.filter(w => w.id === items.id)

The above code returns me all the ids inside the wishlistIds without filtering the id's inside the the items. What is the correct way to approach this problem?

Do you want to get the intersection of both lists? I.e. the ids of all products that are wishlisted and in the current set of items? — Ruben Helsloot
– Ruben Helsloot, Commented Dec 6, 2021 at 23:07
probably one solution is wishlistIds.filter(w =>items.find(item => w.id === item.id) > 0) — Sphinx
– Sphinx, Commented Dec 6, 2021 at 23:11

Phil · Accepted Answer · 2021-12-06 23:17:08Z

3

Create a Set of item IDs and use that to filter the wishlist array

const wishlistIds = [123,425,212,512,516]
const items = [{id:123, productName:"Cheese", price: 15.99}, {id:599, productName: "Honey", price:21.99}]

const itemIds = new Set(items.map(({ id }) => id))

const filteredWishlist = wishlistIds.filter(id => itemIds.has(id))

console.log(filteredWishlist)

I'm using a Set here as Set.prototype.has() is O(1) time complexity as opposed to Array.prototype.includes() which is O(n).

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set#performance

edited Dec 6, 2021 at 23:17

answered Dec 6, 2021 at 23:11

Phil

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Kinglish · Accepted Answer · 2021-12-06 23:10:30Z

2

First filter the list, then map it to get just the ID

let wishlistIds = [123,425,212,512,516]
let items = [{id:123, productName:"Cheese", price: 15.99}, {id:599, productName: "Honey", price:21.99}]
let hearts = items.filter(w => wishlistIds.includes(w.id)).map(w => w.id)
console.log(hearts)

answered Dec 6, 2021 at 23:10

Kinglish

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