How to split a long array into smaller arrays with JavaScript

Question

I have an array of e-mails  it can be just 1 email  or 100 emails   and I need to send the array with an ajax request  that I know how to do   but I can only send an array that has 10 or less e-mails in it  So if there is an original array of 20 e-mails I will need to split them up into 2 arrays of 10 each  or if there are 15 e-mails in the original array  then 1 array of 10  and another array of 5  I m using jQuery  what would be the best way to do this

User · Answer

function chunkArrayInGroups arr  size        var newArr          for  var i 0  i  lt  arr length  i   size       newArr push arr slice i i size              return newArr      chunkArrayInGroups  0  1  2  3  4  5  6   3

User · Answer

You can use lodash  https   lodash com docs    chunk   a    b    c    d    2           a    b      c    d

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const originalArr    1 2 3 4 5 6 7 8 9 10 11   const splittedArray         while  originalArr length  gt  0        splittedArray push originalArr splice 0 range           output for range 3 splittedArray       1 2 3  4 5 6  7 8 9  10 11    output for range 4 splittedArray       1 2 3 4  5 6 7 8  9 10 11

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Here is a simple one liner   x000D   x000D  var segment    arr  n    gt  arr reduce  r e i    gt  i n    r r length-1  push e   r  x000D                                                         r push  e    r        x000D          arr   Array from  length  31   map    i    gt  i 1   x000D  console log segment arr 7    x000D   x000D   x000D

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Another implementation   const arr     H    o    w         t    o         s    p    l    i    t         a         l    o    n    g         a    r    r    a    y         i    n    t    o         s    m    a    l    l    e    r         a    r    r    a    y    s              w    i    t    h         J    a    v    a    S    c    r    i    p    t     const size   3   const res   arr reduce  acc  curr  i    gt      if     i   size             if index is 0 or can be divided by the  size         acc push arr slice i  i   size           push a chunk of the original array to the accumulator       return acc                gt     H    o    w           t    o           s    p      l    i    t           a           l    o    n      g         a      r    r    a      y         i      n    t    o           s    m      a    l    l      e    r           a    r    r      a    y    s                w      i    t    h           J    a      v    a    S      c    r    i      p    t      NB - This does not modify the original array   Or  if you prefer a functional  100  immutable  although there s really nothing bad in mutating in place like done above  and self-contained method   function splitBy size  list      return list reduce  acc  curr  i  self    gt        if     i   size               return                acc            self slice i  i   size                        return acc

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As a supplement to  jyore s answer  and in case you still want to keep the original array     var originalArray    1 2 3 4 5 6 7 8    var splitArray   function  arr  size       var arr2   arr slice 0         arrays          while  arr2 length  gt  0          arrays push arr2 splice 0  size           return arrays     splitArray originalArray  2      originalArray is still    1 2 3 4 5 6 7 8

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Don t use jquery   use plain javascript  var a    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15    var b   a splice 0 10      a is now  11 12 13 14 15     b is now  1 2 3 4 5 6 7 8 9 10     You could loop this to get the behavior you want   var a   YOUR ARRAY  while a length        console log a splice 0 10        This would give you 10 elements at a time   if you have say 15 elements  you would get 1-10  the 11-15 as you wanted

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If you want a method that doesn t modify the existing array  try this   let oldArray    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15   let newArray       let size   3     Size of chunks you are after let j   0     This helps us keep track of the child arrays  for  var i   0  i  lt  oldArray length  i        if  i   size     0        j         if  newArray j   newArray j          newArray j  push oldArray i

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You can take a look at this code   Simple and Effective     function chunkArrayInGroups array  unit    var results       length   Math ceil array length   unit    for  var i   0  i  lt  length  i          results push array slice i   unit   i   1    unit       return results     chunkArrayInGroups   a    b    c    d    2

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as a function  var arrayChunk   function  array  chunkSize                var arrayOfArrays                    if  array length  lt   chunkSize                    arrayOfArrays push array                 else                   for  var i 0  i lt array length  i  chunkSize                        arrayOfArrays push array slice i i chunkSize                                                return arrayOfArrays              to use  arrayChunk originalArray  10    10 being the chunk size

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Another method   var longArray    1  2  3  4  5  6  7  8  9  10   var size   2   var newArray   new Array Math ceil longArray length   size   fill          map function     return this splice 0  size     longArray slice         newArray     1  2    3  4    5  6    7  8    9  10      This doesn t affect the original array as a copy  made using slice  is passed into the  this  argument of map

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using recursion  let myArr    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16   let size   4    Math sqrt myArr length   -- gt  For a n x n matrix let tempArr       function createMatrix arr  i        if  arr length     0          if i   size    0            tempArr push arr splice 0 size                  createMatrix arr  i - 1          createMatrix myArr  myArr length   console log tempArr     Note  The existing array i e  myArr will be modified

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using prototype we can set directly to array class     x000D   x000D  Array prototype chunk   function n    x000D    if   this length    x000D      return     x000D      x000D    return  this slice 0  n   concat this slice n  chunk n    x000D     x000D  console log  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  chunk 5    x000D   x000D   x000D

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function chunkArrayInGroups arr  size        var newArr          for  var i 0  arr length gt size  i         newArr push arr splice 0 size              newArr push arr slice 0        return newArr      chunkArrayInGroups  0  1  2  3  4  5  6   3

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Another implementation  using Array reduce  I think it   s the only one missing     const splitArray    arr  size    gt        if  size     0            return                return arr reduce  split  element  index    gt            index   size     0   split push  element     split Math floor index   size   push element           return split                   As many solutions above  this one   s non-destructive  Returning an empty array when the size is 0 is just a convention  If the if block is omitted you get an error  which might be what you want

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Array reduce could be inefficient for large arrays  especially with the mod operator   I think a cleaner  and possibly easier to read  functional solution would be this   const chunkArray    arr  size    gt    arr length  gt  size        arr slice 0  size      chunkArray arr slice size   size          arr

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Assuming you don t want to destroy the original array  you can use code like this to break up the long array into smaller arrays which you can then iterate over   var longArray            assume this has 100 or more email addresses in it var shortArrays       i  len   for  i   0  len   longArray length  i  lt  len  i    10        shortArrays push longArray slice i  i   10          now you can iterate over shortArrays which is an     array of arrays where each array has 10 or fewer     of the original email addresses in it  for  i   0  len   shortArrays length  i  lt  len  i             shortArrays i  is an array of email addresss of 10 or less

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I would like to share my solution as well  It s a little bit more verbose but works as well   var data    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15    var chunksize   4    var chunks        data forEach  item   gt     if  chunks length    chunks chunks length-1  length    chunksize    chunks push         chunks chunks length-1  push item        console log chunks     Output  formatted        1   2   3   4       5   6   7   8       9  10  11  12      13  14  15

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More compact    x000D   x000D  const chunk    xs  size    gt  x000D    xs map     i    gt  x000D       i   size     0   xs slice i  i   size    null   filter Boolean   x000D       x000D     Usage  x000D  const sampleArray   new Array 33  fill undefined  map     i    gt  i   x000D   x000D  console log chunk sampleArray  5    x000D   x000D   x000D

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var size   10  var arrayOfArrays       for  var i 0  i lt bigarray length  i  size         arrayOfArrays push bigarray slice i i size      console log arrayOfArrays     Unlike splice    slice   is non-destructive to the original array

User · Answer

Just loop over the array  splicing it until it s all consumed     var a     a   b   c   d   e   f   g       chunk  while  a length   0       chunk   a splice 0 3     console log chunk        output      a    b    c       d    e    f       g

[javascript] How to split a long array into smaller arrays, with JavaScript

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