CFP - Docs - pFind

pFind

(predicate: AsyncPredicate) => async (collection: Collection) => Value | undefined

One at a time, asynchronously find the first value that passes a condition

Try It

const gt2 = async n => n > 2
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3]) // is 3
await findGt2([1, 2]) // is undefined
const gt2 = async (n: number) => n > 2
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3]) // is 3
await findGt2([1, 2]) // is undefined

Try It

const gt2 = async n => n > 2
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3]) // is 3
await findGt2([1, 2]) // is undefined
const gt2 = async (n: number) => n > 2
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3]) // is 3
await findGt2([1, 2]) // is undefined

Sometimes we want to asynchronously find a value that passes a condition. Below, we're running an online store. Customers have expressed confusion about discount codes being applied. Let's clarify by showing which item qualifies their order for a code.

Try It

const mockStoreApi = {
  qualifiesForDiscount: async ({ code, item }) =>
    item === 'detergent' && code === 'soft',
}

const shoppingCart = ['broom', 'mop', 'detergent']
const findQualifyingItem = pFind(mockStoreApi.qualifiesForDiscount)
const itemCodeArgs = shoppingCart.map(item => ({ item, code: 'soft' }))
const result = await findQualifyingItem(itemCodeArgs)

if (result) {
  const { code, item } = result
  console.log(`code '${code}' applied because you bought ${item}`)
}
type ItemCode = {
  item: string
  code: string
}

const mockStoreApi = {
  qualifiesForDiscount: async ({ code, item }: ItemCode) =>
    item === 'detergent' && code === 'soft',
}

const shoppingCart = ['broom', 'mop', 'detergent']
const findQualifyingItem = pFind(mockStoreApi.qualifiesForDiscount)<ItemCode[]>
const itemCodeArgs = shoppingCart.map(item => ({ item, code: 'soft' }))
const result = await findQualifyingItem(itemCodeArgs)

if (result) {
  const { code, item } = result
  console.log(`code '${code}' applied because you bought ${item}`)
}

Try It

const mockStoreApi = {
  qualifiesForDiscount: async ({ code, item }) =>
    item === 'detergent' && code === 'soft',
}

const shoppingCart = ['broom', 'mop', 'detergent']
const findQualifyingItem = pFind(
  mockStoreApi.qualifiesForDiscount
)
const itemCodeArgs = shoppingCart.map(item => ({
  item,
  code: 'soft',
}))
const result =
  await findQualifyingItem(itemCodeArgs)

if (result) {
  const { code, item } = result
  console.log(
    `code '${code}' applied because you bought ${item}`
  )
}
type ItemCode = {
  item: string
  code: string
}

const mockStoreApi = {
  qualifiesForDiscount: async ({
    code,
    item,
  }: ItemCode) =>
    item === 'detergent' && code === 'soft',
}

const shoppingCart = ['broom', 'mop', 'detergent']
const findQualifyingItem = pFind(
  mockStoreApi.qualifiesForDiscount
)<ItemCode[]>
const itemCodeArgs = shoppingCart.map(item => ({
  item,
  code: 'soft',
}))
const result =
  await findQualifyingItem(itemCodeArgs)

if (result) {
  const { code, item } = result
  console.log(
    `code '${code}' applied because you bought ${item}`
  )
}

pFind awaits each item before moving onto the next. See async.detectLimit if you want to run more than one call at a time.

Try It

const start = new Date().getTime()

const gt2 = async n => {
  const msPassed = Date.now() - start
  console.log(`ms passed: ${msPassed}, for n = ${n}`)

  await pWaitMs(20)
  return n > 2
}
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)
const start = new Date().getTime()

const gt2 = async (n: number) => {
  const msPassed = Date.now() - start
  console.log(`ms passed: ${msPassed}, for n = ${n}`)

  await pWaitMs(20)
  return n > 2
}
const findGt2 = pFind(gt2)<number[]>

await findGt2([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)

Try It

const start = new Date().getTime()

const gt2 = async n => {
  const msPassed = Date.now() - start
  console.log(
    `ms passed: ${msPassed}, for n = ${n}`
  )

  await pWaitMs(20)
  return n > 2
}
const findGt2 = pFind(gt2)

await findGt2([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)
const start = new Date().getTime()

const gt2 = async (n: number) => {
  const msPassed = Date.now() - start
  console.log(
    `ms passed: ${msPassed}, for n = ${n}`
  )

  await pWaitMs(20)
  return n > 2
}
const findGt2 = pFind(gt2)<number[]>

await findGt2([1, 2, 3])
const totalMsPassed = Date.now() - start
console.log(`total ms passed: ${totalMsPassed}`)