CFP - Docs - mKeepRange

mKeepRange

(range: Range) => (anArray: array) => anArray

Keep a range of elements

Ranges in Common FP are inclusive

Consider keepRange instead.
This is for the uncommon case where mutating anArray is required.

Try It

const range = { startIdx: 1, endIdx: 2 }
const mKeep2ndAnd3rd = mKeepRange(range)

const arr = [1, 2, 3, 4]
const mutatedArr = mKeep2ndAnd3rd(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3]
const range = { startIdx: 1, endIdx: 2 }
const mKeep2ndAnd3rd = mKeepRange(range)

const arr = [1, 2, 3, 4]
const mutatedArr = mKeep2ndAnd3rd(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3]

Try It

const range = { startIdx: 1, endIdx: 2 }
const mKeep2ndAnd3rd = mKeepRange(range)

const arr = [1, 2, 3, 4]
const mutatedArr = mKeep2ndAnd3rd(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3]
const range = { startIdx: 1, endIdx: 2 }
const mKeep2ndAnd3rd = mKeepRange(range)

const arr = [1, 2, 3, 4]
const mutatedArr = mKeep2ndAnd3rd(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3]

Sometimes we want to keep a range of elements. Below, we have the NFL box scores for two Eagles receivers. Let's find their combined total receptions and yards.

Try It

const statsByReciever = [
  ['receiver', 'targets', 'receptions', 'yards', 'touchdowns'],
  ['a.j. brown', 11, 8, 110, 1],
  ['devonta smith', 12, 11, 109, 1],
]

const recAndYds = { startIdx: 2, endIdx: 3 }
const keepRecAndYds = mKeepRange(recAndYds)
const trim = forEach(keepRecAndYds)
trim(statsByReciever)

const statsByMetric = transpose(statsByReciever)
const format = ([metric, ...stats]) => {
  const total = sumValues(stats)
  return `  ${metric}: ${total}`
}
const getTotals = compose([
  mapValues(format),
  prependOne('A.J. Brown and DeVonta Smith combined for'),
  joinValues('\n'),
])
const totals = getTotals(statsByMetric)
console.log(totals)
// prints
// A.J. Brown and DeVonta Smith combined for
//   receptions: 19
//   yards: 219
type Row = Array<string | number>
const statsByReceiver: Row[] = [
  ['receiver', 'targets', 'receptions', 'yards', 'touchdowns'],
  ['a.j. brown', 11, 8, 110, 1],
  ['devonta smith', 12, 11, 109, 1],
]

const recAndYds = { startIdx: 2, endIdx: 3 }
const keepRecAndYds = mKeepRange(recAndYds)<Row>
const trim = forEach(keepRecAndYds)<Row[]>
trim(statsByReceiver)

type MetricStats = [string, ...number[]]
const statsByMetric = transpose(statsByReceiver) as MetricStats[]

const format = (metricStats: MetricStats) => {
  const [metric, ...stats] = metricStats
  const total = sumValues(stats)
  return `  ${metric}: ${total}`
}
const getTotals = compose([
  mapValues(format)<MetricStats[]>,
  prependOne('A.J. Brown and DeVonta Smith combined for'),
  joinValues('\n'),
])
const totals = getTotals(statsByMetric)
console.log(totals)
// prints
// A.J. Brown and DeVonta Smith combined for
//  receptions: 19
//  yards: 219

Try It

const statsByReciever = [
  [
    'receiver',
    'targets',
    'receptions',
    'yards',
    'touchdowns',
  ],
  ['a.j. brown', 11, 8, 110, 1],
  ['devonta smith', 12, 11, 109, 1],
]

const recAndYds = { startIdx: 2, endIdx: 3 }
const keepRecAndYds = mKeepRange(recAndYds)
const trim = forEach(keepRecAndYds)
trim(statsByReciever)

const statsByMetric = transpose(statsByReciever)
const format = ([metric, ...stats]) => {
  const total = sumValues(stats)
  return `  ${metric}: ${total}`
}
const getTotals = compose([
  mapValues(format),
  prependOne(
    'A.J. Brown and DeVonta Smith combined for'
  ),
  joinValues('\n'),
])
const totals = getTotals(statsByMetric)
console.log(totals)
// prints
// A.J. Brown and DeVonta Smith combined for
//   receptions: 19
//   yards: 219
type Row = Array<string | number>
const statsByReceiver: Row[] = [
  [
    'receiver',
    'targets',
    'receptions',
    'yards',
    'touchdowns',
  ],
  ['a.j. brown', 11, 8, 110, 1],
  ['devonta smith', 12, 11, 109, 1],
]

const recAndYds = { startIdx: 2, endIdx: 3 }
const keepRecAndYds = mKeepRange(recAndYds)<Row>
const trim = forEach(keepRecAndYds)<Row[]>
trim(statsByReceiver)

type MetricStats = [string, ...number[]]
const statsByMetric = transpose(
  statsByReceiver
) as MetricStats[]

const format = (metricStats: MetricStats) => {
  const [metric, ...stats] = metricStats
  const total = sumValues(stats)
  return `  ${metric}: ${total}`
}
const getTotals = compose([
  mapValues(format)<MetricStats[]>,
  prependOne(
    'A.J. Brown and DeVonta Smith combined for'
  ),
  joinValues('\n'),
])
const totals = getTotals(statsByMetric)
console.log(totals)
// prints
// A.J. Brown and DeVonta Smith combined for
//  receptions: 19
//  yards: 219