CFP - Docs - discardLastWhile

discardLastWhile

(predicate: Predicate) => (anArray: array) => array

Discard last elements that pass a condition

Try It

const gt2 = n => n > 2
const discardLastWhileGt2 = discardLastWhile(gt2)

discardLastWhileGt2([1, 2, 3, 4]) // is [1, 2]
discardLastWhileGt2([3, 4, 1]) // is [3, 4, 1]
const gt2 = (n: number) => n > 2
const discardLastWhileGt2 = discardLastWhile(gt2)<number[]>

discardLastWhileGt2([1, 2, 3, 4]) // is [1, 2]
discardLastWhileGt2([3, 4, 1]) // is [3, 4, 1]

Try It

const gt2 = n => n > 2
const discardLastWhileGt2 = discardLastWhile(gt2)

discardLastWhileGt2([1, 2, 3, 4]) // is [1, 2]
discardLastWhileGt2([3, 4, 1]) // is [3, 4, 1]
const gt2 = (n: number) => n > 2
const discardLastWhileGt2 = discardLastWhile(gt2)<
  number[]
>

discardLastWhileGt2([1, 2, 3, 4]) // is [1, 2]
discardLastWhileGt2([3, 4, 1]) // is [3, 4, 1]

This is useful when we have sorted data and don't need to filter over all of it. Below, we have a list of online players sorted by gold. Players with over 1,000 gold are obviously cheaters, so let's remove them.

Try It

const players = [
  { name: 'meg', gold: 80 },
  { name: 'tom', gold: 120 },
  { name: 'ken', gold: 9001 },
  { name: 'chris', gold: 9999 },
]

const discardCheaters = discardLastWhile(({ gold }) => gold > 1000)
const updatedPlayers = discardCheaters(players)
console.log(updatedPlayers)
// is [
//   { name: meg, gold: 80 }
//   { name: tom, gold: 120 }
// ]
type Player = { name: string; gold: number }

const players = [
  { name: 'meg', gold: 80 },
  { name: 'tom', gold: 120 },
  { name: 'ken', gold: 9001 },
  { name: 'chris', gold: 9999 },
]

const discardCheaters = discardLastWhile(({ gold }: Player) => gold > 1000)<
  Player[]
>
const updatedPlayers = discardCheaters(players)
console.log(updatedPlayers)
// is [
//   { name: meg, gold: 80 }
//   { name: tom, gold: 120 }
// ]

Try It

const players = [
  { name: 'meg', gold: 80 },
  { name: 'tom', gold: 120 },
  { name: 'ken', gold: 9001 },
  { name: 'chris', gold: 9999 },
]

const discardCheaters = discardLastWhile(
  ({ gold }) => gold > 1000
)
const updatedPlayers = discardCheaters(players)
console.log(updatedPlayers)
// is [
//   { name: meg, gold: 80 }
//   { name: tom, gold: 120 }
// ]
type Player = { name: string; gold: number }

const players = [
  { name: 'meg', gold: 80 },
  { name: 'tom', gold: 120 },
  { name: 'ken', gold: 9001 },
  { name: 'chris', gold: 9999 },
]

const discardCheaters = discardLastWhile(
  ({ gold }: Player) => gold > 1000
)<Player[]>
const updatedPlayers = discardCheaters(players)
console.log(updatedPlayers)
// is [
//   { name: meg, gold: 80 }
//   { name: tom, gold: 120 }
// ]