CFP - Docs - mPrependOne

mPrependOne

(value: any) => (anArray: array) => anArray

Prepend a value to an array

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

Try It

const arr = ['b', 'c']
const prependA = mPrependOne('a')
const mutatedArr = prependA(arr)

console.log(mutatedArr === arr) // is true
console.log(arr) // is ['a', 'b', 'c']
const arr = ['b', 'c']
const prependA = mPrependOne('a')
const mutatedArr = prependA(arr)

console.log(mutatedArr === arr) // is true
console.log(arr) // is ['a', 'b', 'c']

Try It

const arr = ['b', 'c']
const prependA = mPrependOne('a')
const mutatedArr = prependA(arr)

console.log(mutatedArr === arr) // is true
console.log(arr) // is ['a', 'b', 'c']
const arr = ['b', 'c']
const prependA = mPrependOne('a')
const mutatedArr = prependA(arr)

console.log(mutatedArr === arr) // is true
console.log(arr) // is ['a', 'b', 'c']

Sometimes we want to mutate an array by prepending a value. Below, we run a sandwich shop and have prep instructions. Apparently people aren't washing their hands and putting gloves on, so let's prepend that step as a reminder.

Try It

const prepInstructions = {
  bacon: [
    'ensure it is fully thawed',
    'open bag with scissors',
    'place in cambro diagonally',
    'wrap the cambro with saran wrap and lid',
  ],
  tuna: [
    'place dried tuna into bowl',
    'break tuna apart',
    'add half a bag of mayo to bowl',
    'knead mayo into tuna',
  ],
}

const prependGloveStep = mPrependOne('wash hands and put on gloves')
const addGloveStepToAll = forEach(prependGloveStep)
addGloveStepToAll(prepInstructions)

console.log(prepInstructions)
// is {
//   bacon: [
//     wash hands and put on gloves
//     ensure it is fully thawed
//     open bag with scissors
//     place in cambro diagonally
//     wrap the cambro with saran wrap and lid
//   ]
//   tuna: [
//     wash hands and put on gloves
//     place dried tuna into bowl
//     break tuna apart
//     add half a bag of mayo to bowl
//     knead mayo into tuna
//   ]
// }
type PrepInstructions = Record<string, string[]>
const prepInstructions: PrepInstructions = {
  bacon: [
    'ensure it is fully thawed',
    'open bag with scissors',
    'place in cambro diagonally',
    'wrap the cambro with saran wrap and lid',
  ],
  tuna: [
    'place dried tuna into bowl',
    'break tuna apart',
    'add half a bag of mayo to bowl',
    'knead mayo into tuna',
  ],
}

const prependGloveStep = mPrependOne('wash hands and put on gloves')<string[]>
const addGloveStepToAll = forEach(prependGloveStep)<PrepInstructions>
addGloveStepToAll(prepInstructions)

console.log(prepInstructions)
// is {
//   bacon: [
//     wash hands and put on gloves
//     ensure it is fully thawed
//     open bag with scissors
//     place in cambro diagonally
//     wrap the cambro with saran wrap and lid
//   ]
//   tuna: [
//     wash hands and put on gloves
//     place dried tuna into bowl
//     break tuna apart
//     add half a bag of mayo to bowl
//     knead mayo into tuna
//   ]
// }

Try It

const prepInstructions = {
  bacon: [
    'ensure it is fully thawed',
    'open bag with scissors',
    'place in cambro diagonally',
    'wrap the cambro with saran wrap and lid',
  ],
  tuna: [
    'place dried tuna into bowl',
    'break tuna apart',
    'add half a bag of mayo to bowl',
    'knead mayo into tuna',
  ],
}

const prependGloveStep = mPrependOne(
  'wash hands and put on gloves'
)
const addGloveStepToAll = forEach(
  prependGloveStep
)
addGloveStepToAll(prepInstructions)

console.log(prepInstructions)
// is {
//   bacon: [
//     wash hands and put on gloves
//     ensure it is fully thawed
//     open bag with scissors
//     place in cambro diagonally
//     wrap the cambro with saran wrap and lid
//   ]
//   tuna: [
//     wash hands and put on gloves
//     place dried tuna into bowl
//     break tuna apart
//     add half a bag of mayo to bowl
//     knead mayo into tuna
//   ]
// }
type PrepInstructions = Record<string, string[]>
const prepInstructions: PrepInstructions = {
  bacon: [
    'ensure it is fully thawed',
    'open bag with scissors',
    'place in cambro diagonally',
    'wrap the cambro with saran wrap and lid',
  ],
  tuna: [
    'place dried tuna into bowl',
    'break tuna apart',
    'add half a bag of mayo to bowl',
    'knead mayo into tuna',
  ],
}

const prependGloveStep = mPrependOne(
  'wash hands and put on gloves'
)<string[]>
const addGloveStepToAll = forEach(
  prependGloveStep
)<PrepInstructions>
addGloveStepToAll(prepInstructions)

console.log(prepInstructions)
// is {
//   bacon: [
//     wash hands and put on gloves
//     ensure it is fully thawed
//     open bag with scissors
//     place in cambro diagonally
//     wrap the cambro with saran wrap and lid
//   ]
//   tuna: [
//     wash hands and put on gloves
//     place dried tuna into bowl
//     break tuna apart
//     add half a bag of mayo to bowl
//     knead mayo into tuna
//   ]
// }