CFP - Docs - findKey

findKey

(predicate: Predicate) => (collection: EntryCollection) => Key

Find the first key that passes a condition

Try It

const findKeyWhereValGt1 = findKey(val => val > 1)

findKeyWhereValGt1([0, 1, 2]) // is 2
findKeyWhereValGt1([1, 2, 3]) // is 1
findKeyWhereValGt1([0, 1]) // is undefined

findKeyWhereValGt1({ a: 1, b: 2 }) // is 'b'
const findKeyWhereValGt1 = findKey((val: number) => val > 1)

findKeyWhereValGt1([0, 1, 2]) // is 2
findKeyWhereValGt1([1, 2, 3]) // is 1
findKeyWhereValGt1([0, 1]) // is undefined

findKeyWhereValGt1({ a: 1, b: 2 }) // is 'b'

Try It

const findKeyWhereValGt1 = findKey(val => val > 1)

findKeyWhereValGt1([0, 1, 2]) // is 2
findKeyWhereValGt1([1, 2, 3]) // is 1
findKeyWhereValGt1([0, 1]) // is undefined

findKeyWhereValGt1({ a: 1, b: 2 }) // is 'b'
const findKeyWhereValGt1 = findKey(
  (val: number) => val > 1
)

findKeyWhereValGt1([0, 1, 2]) // is 2
findKeyWhereValGt1([1, 2, 3]) // is 1
findKeyWhereValGt1([0, 1]) // is undefined

findKeyWhereValGt1({ a: 1, b: 2 }) // is 'b'

Sometimes we want to find a key based off a condition. Below, we are heading to a cat cafe and want to schedule time to pet a kitten. Let's find one.

Try It

const cats = {
  charlie: { age: 'cat' },
  luna: { age: 'kitten' },
  max: { age: 'old cat' },
  leo: { age: 'kitten' },
}

const findKitten = findKey(cat => cat.age === 'kitten')
const name = findKitten(cats)
console.log(name)
// is luna
type Cat = { age: string }

type Cats = Record<string, Cat>
const cats: Cats = {
  charlie: { age: 'cat' },
  luna: { age: 'kitten' },
  max: { age: 'old cat' },
  leo: { age: 'kitten' },
}

const findKitten = findKey((cat: Cat) => cat.age === 'kitten')<Cats>
const name = findKitten(cats)
console.log(name)
// is luna

Try It

const cats = {
  charlie: { age: 'cat' },
  luna: { age: 'kitten' },
  max: { age: 'old cat' },
  leo: { age: 'kitten' },
}

const findKitten = findKey(
  cat => cat.age === 'kitten'
)
const name = findKitten(cats)
console.log(name)
// is luna
type Cat = { age: string }

type Cats = Record<string, Cat>
const cats: Cats = {
  charlie: { age: 'cat' },
  luna: { age: 'kitten' },
  max: { age: 'old cat' },
  leo: { age: 'kitten' },
}

const findKitten = findKey(
  (cat: Cat) => cat.age === 'kitten'
)<Cats>
const name = findKitten(cats)
console.log(name)
// is luna