CFP - Docs - mapValues

mapValues

(mapperFn: MapperFn) => (collection: Collection) => Collection

Change each value of a collection

Try It

const arr = [1, 2, 3]

const inc = n => n + 1
const incAll = mapValues(inc)
incAll(arr) // is [2, 3, 4]
const arr = [1, 2, 3]

const inc = (n: number) => n + 1
const incAll = mapValues(inc)
incAll(arr) // is [2, 3, 4]

Try It

const arr = [1, 2, 3]

const inc = n => n + 1
const incAll = mapValues(inc)
incAll(arr) // is [2, 3, 4]
const arr = [1, 2, 3]

const inc = (n: number) => n + 1
const incAll = mapValues(inc)
incAll(arr) // is [2, 3, 4]

We often want to change the values of a collection. Below, we're organizing a conference. We have a list of attendees and need their first names for name tags. Let's map the attendees to their first names.

Try It

const attendees = [
  { first: 'liz', last: 'brown' },
  { first: 'phil', last: 'smith' },
  { first: 'mary', last: 'garcia' },
]

const getFirstName = get('first')
const getAllFirstNames = mapValues(getFirstName)
const firstNames = getAllFirstNames(attendees)
console.log(firstNames)
// is [
//   liz,
//   phil,
//   mary,
// ]
type Person = { first: string; last: string }
const attendees: Person[] = [
  { first: 'liz', last: 'brown' },
  { first: 'phil', last: 'smith' },
  { first: 'mary', last: 'garcia' },
]

const getFirstName = get('first')<Person>
const getAllFirstNames = mapValues(getFirstName)<Person[]>
const firstNames = getAllFirstNames(attendees)
console.log(firstNames)
// is [
//   liz,
//   phil,
//   mary,
// ]

Try It

const attendees = [
  { first: 'liz', last: 'brown' },
  { first: 'phil', last: 'smith' },
  { first: 'mary', last: 'garcia' },
]

const getFirstName = get('first')
const getAllFirstNames = mapValues(getFirstName)
const firstNames = getAllFirstNames(attendees)
console.log(firstNames)
// is [
//   liz,
//   phil,
//   mary,
// ]
type Person = { first: string; last: string }
const attendees: Person[] = [
  { first: 'liz', last: 'brown' },
  { first: 'phil', last: 'smith' },
  { first: 'mary', last: 'garcia' },
]

const getFirstName = get('first')<Person>
const getAllFirstNames = mapValues(getFirstName)<
  Person[]
>
const firstNames = getAllFirstNames(attendees)
console.log(firstNames)
// is [
//   liz,
//   phil,
//   mary,
// ]