1. add
    1. #
  2. all
    1. >
    2. C
  3. alter
    1. >
    2. C
  4. any
    1. >
    2. C
  5. append
    1. S
  6. appendAll
    1. >
    2. A
  7. appendOne
    1. A
  8. assignDefaults
    1. >
    2. K
  9. assignOverrides
    1. >
    2. K
  10. compareByPath
  11. compareByProp
  12. compose
    1. >
  13. containedIn
    1. @
  14. contains
    1. >
    2. &
  15. dateIsBetween
    1. D
  16. defaultFalseyValTo
    1. @
  17. defaultNullishValTo
    1. @
  18. discard
    1. >
    2. C
  19. discardFirst
    1. >
    2. Q
  20. discardFirstWhile
    1. >
    2. A
  21. discardLast
    1. >
    2. Q
  22. discardLastWhile
    1. >
    2. A
  23. discardRange
    1. A
  24. discardWhen
    1. >
    2. C
  25. divideBy
    1. #
  26. endsWith
    1. S
  27. expand
    1. >
    2. S
  28. expandEnd
    1. >
    2. S
  29. expandStart
    1. >
    2. S
  30. fillRangeWith
    1. A
  31. fillWith
    1. A
  32. find
    1. C
  33. findKey
    1. E
  34. findKeyWithVal
    1. >
    2. $
  35. findLast
    1. A
  36. findLastKey
    1. >
    2. A
  37. findLastKeyWithVal
    1. >
    2. Q
  38. first
    1. >
    2. Q
  39. flattenFully
    1. A
  40. flattenOnce
    1. A
  41. flattenToDepth
    1. A
  42. forEach
    1. C
  43. get
    1. @
  44. getAtPath
    1. @
  45. getAverageValue
  46. getCommonValues
    1. >
  47. getExclusiveValues
  48. getKeys
    1. E
  49. getMaxValue
    1. C
  50. getMinValue
    1. C
  51. getRandomValue
    1. C
  52. getSize
    1. &
  53. getValueAtMapKey
    1. P
  54. getValues
    1. E
  55. greaterThan
    1. #
  56. greaterThanOrEqualTo
    1. #
  57. groupBy
    1. C
  58. invert
    1. K
  59. invokeWith
    1. F
  60. isAfter
    1. D
  61. isAtOrAfter
    1. D
  62. isAtOrBefore
    1. D
  63. isBefore
    1. D
  64. isEmpty
    1. &
  65. isFalsey
    1. @
  66. isLaden
    1. &
  67. isTruthy
    1. @
  68. joinValues
    1. C
  69. keep
    1. C
  70. keepFirst
    1. >
    2. Q
  71. keepFirstWhile
    1. >
    2. A
  72. keepLast
    1. >
    2. Q
  73. keepLastWhile
    1. >
    2. A
  74. keepRange
    1. Q
  75. keepWhen
    1. C
  76. last
    1. Q
  77. lessThan
    1. #
  78. lessThanOrEqualTo
    1. #
  79. mAppendAll
    1. M
    2. A
  80. mAppendOne
    1. M
    2. A
  81. mAssignDefaults
    1. M
    2. K
  82. mAssignOverrides
    1. M
    2. K
  83. mDiscardFirst
    1. >
    2. M
    3. A
  84. mDiscardFirstWhile
    1. >
    2. M
    3. A
  85. mDiscardLast
    1. >
    2. M
    3. A
  86. mDiscardLastWhile
    1. >
    2. M
    3. A
  87. mDiscardRange
    1. M
    2. A
  88. mFillRangeWith
    1. M
    2. A
  89. mFillWith
    1. M
    2. E
  90. mKeepFirst
    1. >
    2. M
    3. A
  91. mKeepFirstWhile
    1. >
    2. M
    3. A
  92. mKeepLast
    1. >
    2. M
    3. A
  93. mKeepLastWhile
    1. >
    2. M
    3. A
  94. mKeepRange
    1. M
    2. A
  95. mMapValues
    1. M
    2. E
  96. mOmit
    1. M
    2. E
  97. mOrder
    1. M
    2. A
  98. mPick
    1. M
    2. E
  99. mPrependAll
    1. M
    2. A
  100. mPrependOne
    1. M
    2. A
  101. mReverse
    1. M
    2. A
  102. mSet
    1. M
  103. mSetAtPath
    1. M
  104. mShuffle
    1. M
    2. A
  105. mUpdate
    1. M
    2. E
  106. mapKeys
    1. K
  107. mapValues
    1. C
  108. multiplyBy
    1. #
  109. negate
  110. numberIsBetween
    1. #
  111. omit
    1. E
  112. order
    1. A
  113. pAll
    1. >
    2. ǁ
    3. C
  114. pAny
    1. >
    2. ǁ
    3. C
  115. pCompose
    1. >
    2. ǁ
  116. pDiscardWhen
    1. >
    2. ǁ
    3. C
  117. pFind
    1. >
    2. ǁ
    3. C
  118. pForEach
    1. >
    2. ǁ
    3. C
  119. pKeepWhen
    1. >
    2. ǁ
    3. C
  120. pMapValues
    1. >
    2. ǁ
    3. C
  121. pPassThrough
    1. ǁ
  122. pResolveValues
    1. >
    2. ǁ
    3. C
  123. pWaitMs
    1. ǁ
  124. passThrough
  125. peek
    1. >
    2. @
  126. pick
    1. E
  127. prepend
    1. S
  128. prependAll
    1. >
    2. A
  129. prependOne
    1. A
  130. prune
    1. >
    2. S
  131. pruneEnd
    1. >
    2. S
  132. pruneStart
    1. >
    2. S
  133. randomlyKeep
    1. C
  134. replaceAllMatches
    1. >
    2. S
  135. replaceFirstMatch
    1. >
    2. S
  136. returnFirstArg
    1. >
    2. @
  137. returnUndefined
    1. >
  138. reverse
    1. A
  139. roundToNearest
    1. #
  140. set
    1. E
  141. shuffle
    1. A
  142. split
    1. S
  143. splitEvery
    1. >
    2. Q
  144. startsWith
    1. S
  145. strictEquals
    1. @
  146. subtract
    1. #
  147. sumValues
    1. C
  148. swapFirstTwoArgs
    1. F
  149. transpose
    1. >
  150. truncateToNChars
    1. S
  151. truncateToNLines
    1. S
  152. update
    1. E
  153. withDatesAscending
  154. withDatesDescending
  155. withNumbersAscending
  156. withNumbersDescending
  157. withStringsAscending
  158. withStringsDescending

mapKeys

mapKeys

  • (mapperFn: MapperFn) => (collection: KeyedCollection) => KeyedCollection

  1. Change each key of a collection

    Below we have some accounts keyed by id. Let's instead key them by email

    Try It
    const accountsById = {
  j0N7: { id: 'j0N7', email: 'tom@example.com' },
  b5sS: { id: 'b5sS', email: 'ken@example.com' },
  yjdk: { id: 'yjdk', email: 'chris@example.com' },
}

const mapToEmailKeys = mapKeys(get('email'))
const accountsByEmail = mapToEmailKeys(accountsById)

console.log(accountsByEmail)
// is {
//   tom@example.com: {
//     id: j0N7
//     email: tom@example.com
//   }
//   ken@example.com: {
//     id: b5sS
//     email: ken@example.com
//   }
//   chris@example.com: {
//     id: yjdk
//     email: chris@example.com
//   }
// }
type Account = {
  id: string
  email: string
}
type Directory = Record<string, Account>
const accountsById: Directory = {
  j0N7: { id: 'j0N7', email: 'tom@example.com' },
  b5sS: { id: 'b5sS', email: 'ken@example.com' },
  yjdk: { id: 'yjdk', email: 'chris@example.com' },
}

const getEmail = get('email')<Account>
const mapToEmailKeys = mapKeys(getEmail)<Directory>
const accountsByEmail = mapToEmailKeys(accountsById)

console.log(accountsByEmail)
// is {
//   tom@example.com: {
//     id: j0N7
//     email: tom@example.com
//   }
//   ken@example.com: {
//     id: b5sS
//     email: ken@example.com
//   }
//   chris@example.com: {
//     id: yjdk
//     email: chris@example.com
//   }
// }
    Try It
    const accountsById = {
  j0N7: { id: 'j0N7', email: 'tom@example.com' },
  b5sS: { id: 'b5sS', email: 'ken@example.com' },
  yjdk: {
    id: 'yjdk',
    email: 'chris@example.com',
  },
}

const mapToEmailKeys = mapKeys(get('email'))
const accountsByEmail =
  mapToEmailKeys(accountsById)

console.log(accountsByEmail)
// is {
//   tom@example.com: {
//     id: j0N7
//     email: tom@example.com
//   }
//   ken@example.com: {
//     id: b5sS
//     email: ken@example.com
//   }
//   chris@example.com: {
//     id: yjdk
//     email: chris@example.com
//   }
// }
type Account = {
  id: string
  email: string
}
type Directory = Record<string, Account>
const accountsById: Directory = {
  j0N7: { id: 'j0N7', email: 'tom@example.com' },
  b5sS: { id: 'b5sS', email: 'ken@example.com' },
  yjdk: {
    id: 'yjdk',
    email: 'chris@example.com',
  },
}

const getEmail = get('email')<Account>
const mapToEmailKeys = mapKeys(
  getEmail
)<Directory>
const accountsByEmail =
  mapToEmailKeys(accountsById)

console.log(accountsByEmail)
// is {
//   tom@example.com: {
//     id: j0N7
//     email: tom@example.com
//   }
//   ken@example.com: {
//     id: b5sS
//     email: ken@example.com
//   }
//   chris@example.com: {
//     id: yjdk
//     email: chris@example.com
//   }
// }

  2. See 'What' for example code.

    One use case is when we have a collection with multiple unique properties. Different parts of the application may have access to one of these properties, but not all. In these situations, it's helpful to map the collection by the available key.