CFP - Docs - mDiscardFirst

mDiscardFirst

(num: number) => (anArray: array) => anArray

Discard the first num values

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

Try It

const mDiscardFirst2 = mDiscardFirst(2)
const arr = [1, 2, 3, 4]
const mutatedArr = mDiscardFirst2(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [3, 4]
const mDiscardFirst2 = mDiscardFirst(2)
const arr = [1, 2, 3, 4]
const mutatedArr = mDiscardFirst2(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [3, 4]

Try It

const mDiscardFirst2 = mDiscardFirst(2)
const arr = [1, 2, 3, 4]
const mutatedArr = mDiscardFirst2(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [3, 4]
const mDiscardFirst2 = mDiscardFirst(2)
const arr = [1, 2, 3, 4]
const mutatedArr = mDiscardFirst2(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [3, 4]

Sometimes we get data in the form of arrays rather than objects. Below, we have logs with redundant data. Specifically, we only have one server and one realm. Let's remove that data.

Try It

const [_headers, ...logs] = [
  ['server', 'realm', 'time', 'message'],
  ['east3', 'api', '10:00:05', 'user purchased hat'],
  ['east3', 'api', '10:00:06', 'purchase passed audit'],
  ['east3', 'api', '10:00:08', 'error requesting customer data'],
]

const removeServerAndRealm = mDiscardFirst(2)
const trim = forEach(removeServerAndRealm)
trim(logs)
console.log(logs)
// is [
//  ['10:00:05', 'user purchased hat'],
//  ['10:00:06', 'purchase passed audit'],
//  ['10:00:08', 'error requesting customer data'],
// ]
const [_headers, ...logs] = [
  ['server', 'realm', 'timestamp', 'message'],
  ['east3', 'api', '10:00:05', 'user purchased hat'],
  ['east3', 'api', '10:00:06', 'purchase passed audit'],
  ['east3', 'api', '10:00:08', 'error requesting customer data'],
]

const removeServerAndRealm = mDiscardFirst(2)<string[]>
const trim = forEach(removeServerAndRealm)<string[][]>
trim(logs)
console.log(logs)
// is [
//  ['10:00:05', 'user purchased hat'],
//  ['10:00:06', 'purchase passed audit'],
//  ['10:00:08', 'error requesting customer data'],
// ]

Try It

const [_headers, ...logs] = [
  ['server', 'realm', 'time', 'message'],
  [
    'east3',
    'api',
    '10:00:05',
    'user purchased hat',
  ],
  [
    'east3',
    'api',
    '10:00:06',
    'purchase passed audit',
  ],
  [
    'east3',
    'api',
    '10:00:08',
    'error requesting customer data',
  ],
]

const removeServerAndRealm = mDiscardFirst(2)
const trim = forEach(removeServerAndRealm)
trim(logs)
console.log(logs)
// is [
//  ['10:00:05', 'user purchased hat'],
//  ['10:00:06', 'purchase passed audit'],
//  ['10:00:08', 'error requesting customer data'],
// ]
const [_headers, ...logs] = [
  ['server', 'realm', 'timestamp', 'message'],
  [
    'east3',
    'api',
    '10:00:05',
    'user purchased hat',
  ],
  [
    'east3',
    'api',
    '10:00:06',
    'purchase passed audit',
  ],
  [
    'east3',
    'api',
    '10:00:08',
    'error requesting customer data',
  ],
]

const removeServerAndRealm = mDiscardFirst(2)<
  string[]
>
const trim = forEach(removeServerAndRealm)<
  string[][]
>
trim(logs)
console.log(logs)
// is [
//  ['10:00:05', 'user purchased hat'],
//  ['10:00:06', 'purchase passed audit'],
//  ['10:00:08', 'error requesting customer data'],
// ]