Check if every id has an existing object in array

Question

I would like to check if there is an existing object for every id of an array.

const ids = [ 'xxnQt5X8pfbcJMn6i', 'fbcJMn6ixxnQt5X8p' ]
const target = [
  { _id: 'xxnQt5X8pfbcJMn6i' },
  { _id: 'Qt5X8pfbcJMn6ixxn' },
]

In this example I would like to get false, as the second ID (fbcJMn6ixxnQt5X8p) is not existing.

This should return true:

const ids = [ 'xxnQt5X8pfbcJMn6i', 'fbcJMn6ixxnQt5X8p' ]
const target = [
  { _id: 'xxnQt5X8pfbcJMn6i' },
  { _id: 'Qt5X8pfbcJMn6ixxn' },
  { _id: 'fbcJMn6ixxnQt5X8p' },
]

This is what I've tried:

ids.every(id => target.find(element => element._id === id))

@baao I just got it after writing the post. As There is a answer postet I can't delete the post. — user3142695
– user3142695, Commented Jun 7, 2018 at 14:30
Do you want to accept my answer or do you want me to delete my answer? You should really use some though. — baao
– baao, Commented Jun 7, 2018 at 14:31

baao · Accepted Answer · 2018-06-07 14:21:40Z

1

You're pretty close, you need to pass a function instead of an object to find though - and I'd recommend to use some() instead of find if you only want to know about if it exists, rather than you need the object in return.

const ids = [ 'xxnQt5X8pfbcJMn6i', 'fbcJMn6ixxnQt5X8p' ]
const target = [
  { _id: 'xxnQt5X8pfbcJMn6i' },
  { _id: 'Qt5X8pfbcJMn6ixxn' },
  { _id: 'fbcJMn6ixxnQt5X8p' },
]

const allIn = ids.every(id => target.some(({_id}) => id === _id));
console.log(allIn);

answered Jun 7, 2018 at 14:21

baao

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Jonas Wilms · Accepted Answer · 2018-06-07 14:32:22Z

1

With a lot of entries, it might be faster to use a Set (so we get O(n + m) instead of O(n * m)) :

const idSet = new Set(target.map(el => el._id));
const result = ids.every(id => idSet.has(id));

answered Jun 7, 2018 at 14:32

Jonas Wilms

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Comments

Emanuele · Accepted Answer · 2018-06-07 14:38:32Z

0

Since every is itself a checker method it's return true or false through the provided function. So you can simply return false:

const res = const res = ids.every(id => target._id === id); console.log(res);

or true:

const res = ids.every(id => target._id !== id); console.log(res);

answered Jun 7, 2018 at 14:38

Emanuele

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