CFP - Docs - mUpdate

mUpdate

(mapperFns: MapperFns) => (collection: EntryCollection) => collection

Update matching entries via mapper functions

Consider update instead.
This is for the uncommon case where mutating collection is required.

Try It

const obj = { a: 1, b: 2, c: 3 }
const inc = n => n + 1
const dec = n => n - 1
const updateAandC = mUpdate({ a: inc, c: dec })

const mutatedObj = updateAandC(obj)
console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: 2
//   b: 2
//   c: 2
// }
const obj = { a: 1, b: 2, c: 3 }
const inc = (n: number) => n + 1
const dec = (n: number) => n - 1
const updateAandC = mUpdate({ a: inc, c: dec })

const mutatedObj = updateAandC(obj)
console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: 2
//   b: 2
//   c: 2
// }

Try It

const obj = { a: 1, b: 2, c: 3 }
const inc = n => n + 1
const dec = n => n - 1
const updateAandC = mUpdate({ a: inc, c: dec })

const mutatedObj = updateAandC(obj)
console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: 2
//   b: 2
//   c: 2
// }
const obj = { a: 1, b: 2, c: 3 }
const inc = (n: number) => n + 1
const dec = (n: number) => n - 1
const updateAandC = mUpdate({ a: inc, c: dec })

const mutatedObj = updateAandC(obj)
console.log(mutatedObj === obj) // is true
console.log(obj)
// is {
//   a: 2
//   b: 2
//   c: 2
// }

Sometimes we want to mutate entries by updating their values. Below, we are coding a gifting feature on our audiobook platform. Let's test it by gifting Cat's Cradle to Luke.

Try It

const friend = {
  name: 'luke',
  books: ['Player Piano'],
}

const addCatsCradle = mAppendOne("Cat's Cradle")
const giftCatsCradleTo = mUpdate({ books: addCatsCradle })

giftCatsCradleTo(friend)
console.log(friend)
// is {
//   name: luke
//   books: [Player Piano, Cat's Cradle]
// }
type Account = {
  name: string
  books: string[]
}
const friend: Account = {
  name: 'luke',
  books: ['Player Piano'],
}

const addCatsCradle = mAppendOne("Cat's Cradle")
const giftCatsCradleTo = mUpdate({ books: addCatsCradle })<Account>

giftCatsCradleTo(friend)
console.log(friend)
// is {
//   name: luke
//   cart: [cozy gloves, alligator socks
// }

Try It

const friend = {
  name: 'luke',
  books: ['Player Piano'],
}

const addCatsCradle = mAppendOne("Cat's Cradle")
const giftCatsCradleTo = mUpdate({
  books: addCatsCradle,
})

giftCatsCradleTo(friend)
console.log(friend)
// is {
//   name: luke
//   books: [Player Piano, Cat's Cradle]
// }
type Account = {
  name: string
  books: string[]
}
const friend: Account = {
  name: 'luke',
  books: ['Player Piano'],
}

const addCatsCradle = mAppendOne("Cat's Cradle")
const giftCatsCradleTo = mUpdate({
  books: addCatsCradle,
})<Account>

giftCatsCradleTo(friend)
console.log(friend)
// is {
//   name: luke
//   cart: [cozy gloves, alligator socks
// }

An array or map of mapperFns can only update a respective array or map. An object, on the other hand, can update any EntryCollection.

Below shows the array validation.

Try It

const inc = n => n + 1
const dec = n => n - 1

const updateFirstTwo = mUpdate([inc, dec])
const arr = [1, 5, 3]
updateFirstTwo(arr)
console.log(arr) // is [2, 4, 3]

const obj = { a: 1 }
try {
  updateFirstTwo(obj)
} catch (err) {
  console.log(err)
  // prints
  // mUpdate requires argument 'collection' to be an array since you passed an
  // array for 'mapperFns'
}
const inc = (n: number) => n + 1
const dec = (n: number) => n - 1

const updateFirstTwo = mUpdate([inc, dec])
const arr = [1, 5, 3]
updateFirstTwo(arr)
console.log(arr) // is [2, 4, 3]

const obj = { a: 1 }
updateFirstTwo(obj) // ts requires an array

Try It

const inc = n => n + 1
const dec = n => n - 1

const updateFirstTwo = mUpdate([inc, dec])
const arr = [1, 5, 3]
updateFirstTwo(arr)
console.log(arr) // is [2, 4, 3]

const obj = { a: 1 }
try {
  updateFirstTwo(obj)
} catch (err) {
  console.log(err)
  // prints
  // mUpdate requires argument 'collection' to be
  // an array since you passed an array for
  // 'mapperFns'
}
const inc = (n: number) => n + 1
const dec = (n: number) => n - 1

const updateFirstTwo = mUpdate([inc, dec])
const arr = [1, 5, 3]
updateFirstTwo(arr)
console.log(arr) // is [2, 4, 3]

const obj = { a: 1 }
updateFirstTwo(obj) // ts requires an array