CFP - Docs - pForEach

pForEach

(fn: AsyncFunction) => async (collection: Collection) => Collection

Call an async function for each entry.

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

Try It

const log = async n => console.log('n: ' + n)
const logAll = pForEach(log)

await logAll([1, 2, 3])
// prints
// n: 1
// n: 2
// n: 3
const log = async (n: number) => console.log('n: ' + n)
const logAll = pForEach(log)

await logAll([1, 2, 3])
// prints
// n: 1
// n: 2
// n: 3

Try It

const log = async n => console.log('n: ' + n)
const logAll = pForEach(log)

await logAll([1, 2, 3])
// prints
// n: 1
// n: 2
// n: 3
const log = async (n: number) =>
  console.log('n: ' + n)
const logAll = pForEach(log)

await logAll([1, 2, 3])
// prints
// n: 1
// n: 2
// n: 3

Sometimes we want to call an async function for each entry in a collection. Below, we want to track the items in our customer's cart. Let's call our mock store API to track each item.

Try It

const mockStoreApi = {
  trackCartItem: async ({ item, user }) => {
    console.log(`item '${item}' is in ${user}'s cart`)
  },
}

const currentUser = 'luke'
const shoppingCart = ['broom', 'mop', 'detergent']
const trackAllCartItems = pForEach(mockStoreApi.trackCartItem)
const itemUserArgs = shoppingCart.map(item => ({ item, user: currentUser }))
await trackAllCartItems(itemUserArgs)
type ItemUser = {
  item: string
  user: string
}

const mockStoreApi = {
  trackCartItem: async ({ item, user }: ItemUser) => {
    console.log(`item '${item}' is in ${user}'s cart`)
  },
}

const currentUser = 'luke'
const shoppingCart = ['broom', 'mop', 'detergent']
const trackAllCartItems = pForEach(mockStoreApi.trackCartItem)<ItemUser[]>
const itemUserArgs = shoppingCart.map(item => ({ item, user: currentUser }))
await trackAllCartItems(itemUserArgs)

Try It

const mockStoreApi = {
  trackCartItem: async ({ item, user }) => {
    console.log(
      `item '${item}' is in ${user}'s cart`
    )
  },
}

const currentUser = 'luke'
const shoppingCart = ['broom', 'mop', 'detergent']
const trackAllCartItems = pForEach(
  mockStoreApi.trackCartItem
)
const itemUserArgs = shoppingCart.map(item => ({
  item,
  user: currentUser,
}))
await trackAllCartItems(itemUserArgs)
type ItemUser = {
  item: string
  user: string
}

const mockStoreApi = {
  trackCartItem: async ({
    item,
    user,
  }: ItemUser) => {
    console.log(
      `item '${item}' is in ${user}'s cart`
    )
  },
}

const currentUser = 'luke'
const shoppingCart = ['broom', 'mop', 'detergent']
const trackAllCartItems = pForEach(
  mockStoreApi.trackCartItem
)<ItemUser[]>
const itemUserArgs = shoppingCart.map(item => ({
  item,
  user: currentUser,
}))
await trackAllCartItems(itemUserArgs)

pForEach calls the function for all entries at once. See async.eachOfLimit if you want to limit the concurrency.

Try It

const start = new Date().getTime()

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

  await pWaitMs(20)
}
const logMsPassedForAll = pForEach(logMsPassed)

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

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

  await pWaitMs(20)
}
const logMsPassedForAll = pForEach(logMsPassed)<number[]>

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

Try It

const start = new Date().getTime()

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

  await pWaitMs(20)
}
const logMsPassedForAll = pForEach(logMsPassed)

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

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

  await pWaitMs(20)
}
const logMsPassedForAll = pForEach(logMsPassed)<
  number[]
>

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