CFP - Docs - pMapValues

pMapValues

(mapperFn: AsyncMapperFn) => async (collection: Collection) => Collection

Asynchronously map the values of a collection.

The mapper function is called for all entries at once. See Notes for an example.

Try It

const inc = async n => n + 1
const incAll = pMapValues(inc)

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

await incAll([1, 2, 3]) // is [2, 3, 4]

Try It

const inc = async n => n + 1
const incAll = pMapValues(inc)

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

await incAll([1, 2, 3]) // is [2, 3, 4]

Sometimes we want to asynchronously map the values of a collection. Below, let's call our mock store API to estimate the shipping for each item in our cart.

Try It

const mockShippingEstimates = {
  broom: '2 days',
  mop: '5 days',
  detergent: '1 day',
}

const mockStoreApi = {
  estimateShipping: async ({ item, destination }) => {
    const shipping = mockShippingEstimates[item]
    return { item, destination, shipping }
  },
}

const userLocation = 'cleveland'
const shoppingCart = ['broom', 'mop', 'detergent']
const estimateShippingPerItem = pMapValues(mockStoreApi.estimateShipping)
const itemDestinationArgs = shoppingCart.map(item => ({
  item,
  destination: userLocation,
}))
const cartWithShipping = await estimateShippingPerItem(itemDestinationArgs)
console.log(cartWithShipping)
// prints
// [
//   {
//     item: broom
//     destination: cleveland
//     shipping: 2 days
//   },
//   {
//     item: mop
//     destination: cleveland
//     shipping: 5 days
//   },
//   {
//     item: detergent
//     destination: cleveland
//     shipping: 1 day
//   },
// ]
type ItemDestination = {
  item: string
  destination: string
}

const mockShippingEstimates: Record<string, string> = {
  broom: '2 days',
  mop: '5 days',
  detergent: '1 day',
}

const mockStoreApi = {
  estimateShipping: async ({ item, destination }: ItemDestination) => {
    const shipping = mockShippingEstimates[item]
    return { item, destination, shipping }
  },
}

const userLocation = 'cleveland'
const shoppingCart = ['broom', 'mop', 'detergent']
const estimateShippingPerItem = pMapValues(mockStoreApi.estimateShipping)<
  ItemDestination[]
>
const itemDestinationArgs = shoppingCart.map(item => ({
  item,
  destination: userLocation,
}))
const cartWithShipping = await estimateShippingPerItem(itemDestinationArgs)
console.log(cartWithShipping)
// prints
// [
//   {
//     item: broom
//     destination: cleveland
//     shipping: 2 days
//   },
//   {
//     item: mop
//     destination: cleveland
//     shipping: 5 days
//   },
//   {
//     item: detergent
//     destination: cleveland
//     shipping: 1 day
//   },
// ]

Try It

const mockShippingEstimates = {
  broom: '2 days',
  mop: '5 days',
  detergent: '1 day',
}

const mockStoreApi = {
  estimateShipping: async ({
    item,
    destination,
  }) => {
    const shipping = mockShippingEstimates[item]
    return { item, destination, shipping }
  },
}

const userLocation = 'cleveland'
const shoppingCart = ['broom', 'mop', 'detergent']
const estimateShippingPerItem = pMapValues(
  mockStoreApi.estimateShipping
)
const itemDestinationArgs = shoppingCart.map(
  item => ({
    item,
    destination: userLocation,
  })
)
const cartWithShipping =
  await estimateShippingPerItem(
    itemDestinationArgs
  )
console.log(cartWithShipping)
// prints
// [
//   {
//     item: broom
//     destination: cleveland
//     shipping: 2 days
//   },
//   {
//     item: mop
//     destination: cleveland
//     shipping: 5 days
//   },
//   {
//     item: detergent
//     destination: cleveland
//     shipping: 1 day
//   },
// ]
type ItemDestination = {
  item: string
  destination: string
}

const mockShippingEstimates: Record<
  string,
  string
> = {
  broom: '2 days',
  mop: '5 days',
  detergent: '1 day',
}

const mockStoreApi = {
  estimateShipping: async ({
    item,
    destination,
  }: ItemDestination) => {
    const shipping = mockShippingEstimates[item]
    return { item, destination, shipping }
  },
}

const userLocation = 'cleveland'
const shoppingCart = ['broom', 'mop', 'detergent']
const estimateShippingPerItem = pMapValues(
  mockStoreApi.estimateShipping
)<ItemDestination[]>
const itemDestinationArgs = shoppingCart.map(
  item => ({
    item,
    destination: userLocation,
  })
)
const cartWithShipping =
  await estimateShippingPerItem(
    itemDestinationArgs
  )
console.log(cartWithShipping)
// prints
// [
//   {
//     item: broom
//     destination: cleveland
//     shipping: 2 days
//   },
//   {
//     item: mop
//     destination: cleveland
//     shipping: 5 days
//   },
//   {
//     item: detergent
//     destination: cleveland
//     shipping: 1 day
//   },
// ]

pMapValues calls the mapper function for all entries at once. See async.mapLimit if you want to limit the concurrency.

Try It

const start = new Date().getTime()

const inc = async n => {
  const msPassed = Date.now() - start
  console.log(`ms passed: ${msPassed}, for n = ${n}`)

  await pWaitMs(20)
  return n + 1
}
const incAll = pMapValues(inc)

await incAll([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)
const start = new Date().getTime()

const inc = async (n: number) => {
  const msPassed = Date.now() - start
  console.log(`ms passed: ${msPassed}, for n = ${n}`)

  await pWaitMs(20)
  return n + 1
}
const incAll = pMapValues(inc)<number[]>

await incAll([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)

Try It

const start = new Date().getTime()

const inc = async n => {
  const msPassed = Date.now() - start
  console.log(
    `ms passed: ${msPassed}, for n = ${n}`
  )

  await pWaitMs(20)
  return n + 1
}
const incAll = pMapValues(inc)

await incAll([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)
const start = new Date().getTime()

const inc = async (n: number) => {
  const msPassed = Date.now() - start
  console.log(
    `ms passed: ${msPassed}, for n = ${n}`
  )

  await pWaitMs(20)
  return n + 1
}
const incAll = pMapValues(inc)<number[]>

await incAll([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)