Compare 2 arrays which returns difference

Question

What s the fastest best way to compare two arrays and return the difference  Much like array diff in PHP  Is there an easy function or am I going to have to create one via each    or a foreach loop

User · Accepted Answer

Working demo http   jsfiddle net u9xES   Good link  Jquery Documentation   http   docs jquery com Main Page  you can search or read APIs here   Hope this will help you if you are looking to do it in JQuery   The alert in the end prompts the array of uncommon element Array i e  difference between 2 array   Please lemme know if I missed anything  cheers   Code  var array1    1  2  3  4  5  6   var array2    1  2  3  4  5  6  7  8  9   var difference        jQuery grep array2  function el            if  jQuery inArray el  array1     -1  difference push el        alert   the difference is     difference       Changed variable name

User · Answer

use underscore as      difference array1 array2

User · Answer

This should work with unsorted arrays  double values and different orders and length  while giving you the filtered values form array1  array2  or both   function arrayDiff arr1  arr2        var diff            diff arr1   arr1 filter function value            if  arr2 indexOf value      -1                return value                         diff arr2   arr2 filter function value            if  arr1 indexOf value      -1                return value                         diff concat   diff arr1 concat diff arr2        return diff      var firstArray    1 2 3 4   var secondArray    4 6 1 4    console log  arrayDiff firstArray  secondArray     console log  arrayDiff firstArray  secondArray  arr1         gt    2  3   console log  arrayDiff firstArray  secondArray  concat         gt    2  3  6

User · Answer

var arrayDiff   function  firstArr  secondArr        var i  o       fLen   firstArr length  sLen   secondArr length  len        if  fLen  gt  sLen            len   sLen        else if  fLen  lt  sLen            len   fLen        else           len   sLen            for  i 0  i  lt  len  i              if  firstArr i      secondArr i                 o push  idx  i  elem1  firstArr i   elem2  secondArr i        idx  array index                      if  fLen  gt  sLen        first  gt  second         for  i sLen  i lt  fLen  i                  o push  idx  i  0  firstArr i   1  undefined                    else if  fLen  lt  sLen            for  i fLen  i lt  sLen  i                  o push  idx  i  0  undefined  1  secondArr i                              return o

User · Answer

The short version can be like this   const diff    a  b    gt  b filter  i    gt  a indexOf i      -1     result   diff   a    b      a    b    c    d        c    d

User · Answer

I know this is an old question  but I thought I would share this little trick   var diff     old array  not new array  get      diff now contains what was in old array that is not in new array

User · Answer

if you also want to compare the order of the answer you can extend the answer to something like this   Array prototype compareTo   function  array2       var array1   this      var difference             grep array2  function el            if    inArray el  array1     -1  difference push el               if  difference length     0            var  i   0          while  i  lt  array1 length               if array1  i      array2  i                    return false                             i                      return true            return false

User · Answer

In this way you don t need to worry about if the first array is smaller than the second one   var arr1    1  2  3  4  5  6 10       arr2    1  2  3  4  5  6  7  8  9    function array diff array1  array2       var difference     grep array1  function el    return   inArray el array2   lt  0        return difference concat   grep array2  function el    return   inArray el array1   lt  0         console log array diff arr1  arr2

User · Answer

SUBTRACT ARRAYS     function subtractarrays array1  array2       var difference           for  var i   0  i  lt  array1 length  i               if    inArray  array1 i   array2      -1                         difference push array1 i                         return difference         You can then call the function anywhere in your code   var I like        love    sex    food    var she likes     love    food     alert   what I like and she does t like is      subtractarrays  I like  she likes        returns  Naughty     This works in all cases and avoids the problems in the methods above  Hope that helps

User · Answer

Array operations like this is not jQuery s strongest point  You should consider a library such as Underscorejs  specifically the difference function

[javascript] Compare 2 arrays which returns difference

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