CFP - Docs - startsWith

startsWith

(prefix: string) => (aString: string) => boolean

Test if one string starts with another

Try It

const startsWithAB = startsWith('ab')

startsWithAB('abcd') // is true
startsWithAB('cdab') // is false
const startsWithAB = startsWith('ab')

startsWithAB('abcd') // is true
startsWithAB('cdab') // is false

Try It

const startsWithAB = startsWith('ab')

startsWithAB('abcd') // is true
startsWithAB('cdab') // is false
const startsWithAB = startsWith('ab')

startsWithAB('abcd') // is true
startsWithAB('cdab') // is false

Sometimes we want to see if a string starts with another. Below, someone turned in a lost notebook with only a first name, 'Chris.'. Let's find which classes have a Chris.

Try It

const classrooms = {
  A: ['ken roberts', 'chris reyes', 'liz brown'],
  B: ['phil smith', 'mary garcia', 'sarah miller'],
  C: ['matt davis', 'chris taylor', 'amy moore'],
}

const startsWithChris = startsWith('chris ')
const roomHasChris = any(startsWithChris)
const getRoomsWithChris = compose([keepWhen(roomHasChris), Object.keys])

const roomsToCheck = getRoomsWithChris(classrooms)
console.log(roomsToCheck) // is [A, C]
type Classrooms = Record<string, string[]>
const classrooms: Classrooms = {
  A: ['ken roberts', 'chris reyes', 'liz brown'],
  B: ['phil smith', 'mary garcia', 'sarah miller'],
  C: ['matt davis', 'chris taylor', 'amy moore'],
}

const startsWithChris = startsWith('chris ')
const roomHasChris = any(startsWithChris)<string[]>
const getRoomsWithChris = compose([
  keepWhen(roomHasChris)<Classrooms>,
  Object.keys,
])

const roomsToCheck = getRoomsWithChris(classrooms)
console.log(roomsToCheck) // is [A, C]

Try It

const classrooms = {
  A: ['ken roberts', 'chris reyes', 'liz brown'],
  B: [
    'phil smith',
    'mary garcia',
    'sarah miller',
  ],
  C: ['matt davis', 'chris taylor', 'amy moore'],
}

const startsWithChris = startsWith('chris ')
const roomHasChris = any(startsWithChris)
const getRoomsWithChris = compose([
  keepWhen(roomHasChris),
  Object.keys,
])

const roomsToCheck = getRoomsWithChris(classrooms)
console.log(roomsToCheck) // is [A, C]
type Classrooms = Record<string, string[]>
const classrooms: Classrooms = {
  A: ['ken roberts', 'chris reyes', 'liz brown'],
  B: [
    'phil smith',
    'mary garcia',
    'sarah miller',
  ],
  C: ['matt davis', 'chris taylor', 'amy moore'],
}

const startsWithChris = startsWith('chris ')
const roomHasChris = any(startsWithChris)<
  string[]
>
const getRoomsWithChris = compose([
  keepWhen(roomHasChris)<Classrooms>,
  Object.keys,
])

const roomsToCheck = getRoomsWithChris(classrooms)
console.log(roomsToCheck) // is [A, C]