How to merge two arrays of objects by ID using lodash

Question

I have two array with one common field member  how can I merge theme easily   For example   var arr1         member    ObjectId  57989cbe54cf5d2ce83ff9d6       bank    ObjectId  575b052ca6f66a5732749ecc       country    ObjectId  575b0523a6f66a5732749ecb           member    ObjectId  57989cbe54cf5d2ce83ff9d8       bank    ObjectId  575b052ca6f66a5732749ecc       country    ObjectId  575b0523a6f66a5732749ecb        var arr2           member    ObjectId  57989cbe54cf5d2ce83ff9d6         name     xxxxxx        age    25           member    ObjectId  57989cbe54cf5d2ce83ff9d8         name     yyyyyyyyyy        age    26       Expected   var merge         member    ObjectId  57989cbe54cf5d2ce83ff9d6       bank    ObjectId  575b052ca6f66a5732749ecc       country    ObjectId  575b0523a6f66a5732749ecb       name     xxxxxx      age    25         member    ObjectId  57989cbe54cf5d2ce83ff9d8       bank    ObjectId  575b052ca6f66a5732749ecc       country    ObjectId  575b0523a6f66a5732749ecb       name     yyyyyyyyyy      age    26       I tried   var merge     unionBy arr1  arr2   member      but not merged as expected  shown array1 value  can any one help me

User · Answer

If both arrays are in the correct order  where each item corresponds to its associated member identifier then you can simply use   var merge     merge arr1  arr2     Which is the short version of   var merge     chain arr1  zip arr2  map function item        return   merge apply null  item      value      Or  if the data in the arrays is not in any particular order  you can look up the associated item by the member value   var merge     map arr1  function item        return   merge item    find arr2     member    item member            You can easily convert this to a mixin  See the example below    x000D   x000D    mixin   x000D     mergeByKey    function arr1  arr2  key    x000D      var criteria       x000D      criteria key    null  x000D      return   map arr1  function item    x000D        criteria key    item key   x000D        return   merge item    find arr2  criteria    x000D          x000D      x000D      x000D   x000D  var arr1      x000D     member    ObjectId  57989cbe54cf5d2ce83ff9d6     x000D     bank    ObjectId  575b052ca6f66a5732749ecc     x000D     country    ObjectId  575b0523a6f66a5732749ecb    x000D       x000D     member    ObjectId  57989cbe54cf5d2ce83ff9d8     x000D     bank    ObjectId  575b052ca6f66a5732749ecc     x000D     country    ObjectId  575b0523a6f66a5732749ecb    x000D      x000D   x000D  var arr2      x000D     member    ObjectId  57989cbe54cf5d2ce83ff9d8     x000D     name    yyyyyyyyyy   x000D     age   26 x000D       x000D     member    ObjectId  57989cbe54cf5d2ce83ff9d6     x000D     name    xxxxxx   x000D     age   25 x000D      x000D   x000D  var arr3     mergeByKey arr1  arr2   member    x000D   x000D  document body innerHTML   JSON stringify arr3  null  4   x000D  body   font-family  monospace  white-space  pre    x000D   lt script src  https   cdnjs cloudflare com ajax libs lodash js 4 14 0 lodash min js  gt  lt  script gt  x000D   x000D   x000D

User · Answer

Create dictionaries for both arrays using   keyBy    merge the dictionaries  and convert the result to an array with   values    In this way  the order of the arrays doesn t matter  In addition  it can also handle arrays of different length    x000D   x000D  const ObjectId    id    gt  id     mock of ObjectId x000D  const arr1      member    ObjectId  57989cbe54cf5d2ce83ff9d8    bank    ObjectId  575b052ca6f66a5732749ecc    country    ObjectId  575b0523a6f66a5732749ecb      member    ObjectId  57989cbe54cf5d2ce83ff9d6    bank    ObjectId  575b052ca6f66a5732749ecc    country    ObjectId  575b0523a6f66a5732749ecb      x000D  const arr2      member    ObjectId  57989cbe54cf5d2ce83ff9d6    name     xxxxxx   age    25    member    ObjectId  57989cbe54cf5d2ce83ff9d8    name     yyyyyyyyyy   age    26    x000D   x000D  const merged     arr1     start sequence x000D     keyBy  member      create a dictionary of the 1st array x000D     merge   keyBy arr2   member       create a dictionary of the 2nd array  and merge it to the 1st x000D     values      turn the combined dictionary to array x000D     value       get the value  array  out of the sequence x000D   x000D  console log merged   x000D   lt script src  https   cdnjs cloudflare com ajax libs lodash js 4 14 0 lodash min js  gt  lt  script gt  x000D   x000D   x000D    Using ES6 Map  Concat the arrays  and reduce the combined array to a Map  Use Object assign to combine objects with the same member to a new object  and store in map  Convert the map to an array with Map values and spread    x000D   x000D  const ObjectId    id    gt  id     mock of ObjectId x000D  const arr1      member    ObjectId  57989cbe54cf5d2ce83ff9d8    bank    ObjectId  575b052ca6f66a5732749ecc    country    ObjectId  575b0523a6f66a5732749ecb      member    ObjectId  57989cbe54cf5d2ce83ff9d6    bank    ObjectId  575b052ca6f66a5732749ecc    country    ObjectId  575b0523a6f66a5732749ecb      x000D  const arr2      member    ObjectId  57989cbe54cf5d2ce83ff9d6    name     xxxxxx   age    25    member    ObjectId  57989cbe54cf5d2ce83ff9d8    name     yyyyyyyyyy   age    26    x000D   x000D  const merged       arr1 concat arr2  reduce  m  o    gt   x000D    m set o member  Object assign m get o member         o   x000D    new Map    values     x000D   x000D  console log merged   x000D   x000D   x000D

[javascript] How to merge two arrays of objects by ID using lodash?

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