CFP - Docs - keep

keep

(values: ValueCollection) => (collection: Collection) => Collection

Keep all values in the collection.

Try It

const keepOnesAndTwos = keep([1, 2])

keepOnesAndTwos([1, 2, 3, 4, 1]) // is [1, 2, 1]
const keepOnesAndTwos = keep([1, 2])

keepOnesAndTwos([1, 2, 3, 4, 1]) // is [1, 2, 1]

Try It

const keepOnesAndTwos = keep([1, 2])

keepOnesAndTwos([1, 2, 3, 4, 1]) // is [1, 2, 1]
const keepOnesAndTwos = keep([1, 2])

keepOnesAndTwos([1, 2, 3, 4, 1]) // is [1, 2, 1]

Sometimes we only want certain values. Below, we have some weekly volunteers at the cat shelter. The weekend helpers' jobs are especially difficult, so let's list their names for "thank you" cards.

Try It

const volunteers = {
  jason: 'saturday',
  amy: 'wednesday',
  kim: 'saturday',
  grace: 'tuesday',
  sam: 'sunday',
}

const keepWeekendHelpers = keep(['saturday', 'sunday'])
const getWeekendHelpers = compose([keepWeekendHelpers, Object.keys])

const weekendHelpers = getWeekendHelpers(volunteers)
console.log(weekendHelpers)
// is [
//  jason
//  kim
//  sam
// ]
type Volunteers = Record<string, string>
const volunteers = {
  jason: 'saturday',
  amy: 'wednesday',
  kim: 'saturday',
  grace: 'tuesday',
  sam: 'sunday',
}

const keepWeekendHelpers = keep(['saturday', 'sunday'])<Volunteers>
const getWeekendHelpers = compose([keepWeekendHelpers, Object.keys])

const weekendHelpers = getWeekendHelpers(volunteers)
console.log(weekendHelpers)
// is [
//  jason
//  kim
//  sam
// ]

Try It

const volunteers = {
  jason: 'saturday',
  amy: 'wednesday',
  kim: 'saturday',
  grace: 'tuesday',
  sam: 'sunday',
}

const keepWeekendHelpers = keep([
  'saturday',
  'sunday',
])
const getWeekendHelpers = compose([
  keepWeekendHelpers,
  Object.keys,
])

const weekendHelpers =
  getWeekendHelpers(volunteers)
console.log(weekendHelpers)
// is [
//  jason
//  kim
//  sam
// ]
type Volunteers = Record<string, string>
const volunteers = {
  jason: 'saturday',
  amy: 'wednesday',
  kim: 'saturday',
  grace: 'tuesday',
  sam: 'sunday',
}

const keepWeekendHelpers = keep([
  'saturday',
  'sunday',
])<Volunteers>
const getWeekendHelpers = compose([
  keepWeekendHelpers,
  Object.keys,
])

const weekendHelpers =
  getWeekendHelpers(volunteers)
console.log(weekendHelpers)
// is [
//  jason
//  kim
//  sam
// ]