How can I convert the arguments object to an array in JavaScript

Question

The arguments object in JavaScript is an odd wart   it acts just like an array in most situations  but it s not actually an array object  Since it s really something else entirely  it doesn t have the useful functions from Array prototype like forEach  sort  filter  and map   It s trivially easy to construct a new array from an arguments object with a simple for loop  For example  this function sorts its arguments   function sortArgs         var args           for  var i   0  i  lt  arguments length  i            args i    arguments i       return args sort        However  this is a rather pitiful thing to have to do simply to get access to the extremely useful JavaScript array functions  Is there a built-in way to do it using the standard library

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function sortArg    var args   Array from arguments   return args sort         x000D   x000D   function sortArg    x000D      var args   Array from arguments    x000D      return args sort    x000D        x000D    x000D   console log sortArg  a    b   1  2   34   88  20   19   39   d    z    ak    bu   90    x000D   x000D   x000D

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Benshmarck 3 methods    function test       console log arguments length     Argument s        var i   0    var loop   1000000    var t   Date now      while i  lt  loop            Array prototype slice call arguments  0          i          console log Date now   - t       i   0    t   Date now      while i  lt  loop            Array apply null  arguments         i          console log Date now   - t      i   0    t   Date now      while i  lt  loop            arguments length    1    arguments 0     Array apply null  arguments         i          console log Date now   - t      test    test 42   test 42  44   test 42  44  88  64  10  64  700  15615156  4654  9   test 42   truc   44   47   454  88  64    ehuehe   10  64  700  15615156  4654  9 97 4 94 56 8 456 156 1 456 867 5 152489 74 5 48479 89 897 894 894 8989 489 489 4 489 488989 498498     RESULT   0 Argument s  256 329 332 1 Argument s  307 418 4 2 Argument s  375 364 367 10 Argument s  962 601 604 40 Argument s  3095 1264 1260   Enjoy

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Lodash   var args     toArray arguments     in action    function    console log   toArray arguments  splice 1       1  2  3    produces    2 3

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In ECMAScript 6 there s no need to use ugly hacks like Array prototype slice    You can instead use spread syntax          x000D   x000D   function     x000D    console log     arguments    x000D    1  2  3   x000D   x000D   x000D    It may look strange  but it s fairly simple  It just extracts arguments  elements and put them back into the array  If you still don t understand  see this examples    x000D   x000D  console log  1      2  3   4    x000D  console log      1  2  3     x000D  console log              1       x000D   x000D   x000D    Note that it doesn t work in some older browsers like IE 11  so if you want to support these browsers  you should use Babel

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It s also worth referencing this Bluebird promises library wiki page that shows how to manage the arguments object into array in a way that makes the function optimizable under V8 JavaScript engine   function doesntLeakArguments         var args   new Array arguments length       for var i   0  i  lt  args length    i            args i    arguments i             return args      This method is used in favor of var args      slice call arguments    The author also shows how a build step can help reduce the verbosity

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This is a very old question  but I think I have a solution that is slightly easier to type than previous solutions and doesn t rely on external libraries   function sortArguments       return Array apply null  arguments  sort

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Try using Object setPrototypeOf    Explanation  Set prototype of arguments to Array prototype   x000D   x000D  function toArray     x000D    return Object setPrototypeOf arguments  Array prototype  x000D     x000D   x000D  console log toArray  abc   123   def 456    0  7  14      x000D   x000D   x000D      Explanation  Take each index of arguments   place item into an array at corresponding index of array   could alternatively use Array prototype map     x000D   x000D  function toArray     x000D    return    map call arguments     k a    gt  a k   x000D     x000D   x000D  console log toArray  abc   123   def 456    0  7  14      x000D   x000D   x000D      Explanation  Take each index of arguments   place item into an array at corresponding index of array   for  of loop   x000D   x000D  function toArray     x000D   let arr       for  let prop of arguments  arr push prop   return arr x000D     x000D   x000D  console log toArray  abc   123   def 456    0  7  14      x000D   x000D   x000D      or Object create    Explanation  Create object  set properties of object to items at each index of arguments  set prototype of created object to Array prototype   x000D   x000D  function toArray     x000D    var obj       x000D    for  var prop in arguments    x000D      obj prop      x000D        value  arguments prop   x000D        writable  true  x000D        enumerable  true  x000D        configurable  true x000D        x000D       x000D    return Object create Array prototype  obj   x000D    x000D   x000D  console log toArray  abc   123   def  456    0   7   14      x000D   x000D   x000D

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function x       var rest       arguments   console log rest  return         rest constructor       x 1 2 3    I tried simple destructing technique

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You can create a reusable function to do it with any arguments  the simplest one is something like this    function sortArgs       return     arguments  sort       sortArgs  ali    reza   1  2   a       1  2   a    ali    reza      Spread syntax can be used in ES6 and above      But if you d like to use something compatible with ES5 and below  you can use Array prototype slice call  so you code looks like this   function sortArgs       return Array prototype slice call arguments  sort       sortArgs  ali    reza   1  2   a       1  2   a    ali    reza      There are also few other ways to do this  for Example using Array from or loop through the arguments and assign them to a new array

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function sortArgs    return    slice call arguments  sort         Returns the arguments object itself function sortArgs    return    sort call arguments      Some array methods are intentionally made not to require the target object to be an actual array  They only require the target to have a property named length and indices  which must be zero or larger integers       sort call  0 1  1 0  length 2        gt    0 0  1 1  length 2

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If you re using jQuery  the following is a good deal easier to remember in my opinion   function sortArgs      return   makeArray arguments  sort

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Although rest parameters work well  if you want to continue to use arguments for some reason  consider  function sortArgs       return     arguments  sort           arguments  can be considered a sort of alternative to Array from arguments   which also works perfectly well    An ES7 alternative is an array comprehension    for  i of arguments  i  sort     This could be easiest if you want to process or filter the arguments prior to sorting    for  i of arguments  if  i   2  Math log i   sort

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Use Array from    which takes an array-like object  such as arguments  as argument and converts it to array    x000D   x000D   function     x000D    console log Array from arguments    x000D    1  2  3    x000D   x000D   x000D    Note that it doesn t work in some older browsers like IE 11  so if you want to support these browsers  you should use Babel

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Another Answer   Use Black Magic Spells   function sortArguments       arguments   proto     Array prototype    return arguments slice   sort        Firefox  Chrome  Node js  IE11 are OK

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I recommend using ECMAScript 6 spread operator  which will Bind trailing parameters to an array  With this solution you don t need to touch the arguments object and your code will be simplified  The downside of this solution is that it does not work across most browsers  so instead you will have to use a JS compiler such as Babel  Under the hood Babel transforms arguments into a Array with a for loop      function sortArgs    args      return args sort        If you can not use a ECMAScript 6  I recommend looking at some of the other answers such as  Jonathan Fingland  function sortArgs         var args   Array prototype slice call arguments       return args sort

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Here s a clean and concise solution    x000D   x000D  function argsToArray     x000D    return Object values arguments   x000D    x000D   x000D     example usage x000D  console log  x000D    argsToArray 1  2  3  4  5  x000D     map arg   gt  arg 11  x000D     x000D   x000D   x000D    Object values    will return the values of an object as an array  and since arguments is an object  it will essentially convert arguments into an array  thus providing you with all of an array s helper functions such as map  forEach  filter  etc

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Here is benchmark of several methods converting arguments into array    As for me  the best solution for small amount of arguments is   function sortArgs       var q         for  var k   0  l   arguments length  k  lt  l  k         q k    arguments k         return q sort        For other cases   function sortArgs     return Array apply null  arguments  sort

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The Arguments object is only available inside a function body  Although you can index the Arguments Object like an array  it is not an array  It does not have any array properties other than length     x000D   x000D     function arguments length 5 x000D  function properties a b c d e   x000D  var function name  arguments callee name x000D  var arguments length  arguments length  x000D  var properties length   properties length   x000D  var function from  properties caller name  x000D  console log  I am the function name     function name   x000D  console log  I am the function length  I am function spacific     properties length    x000D  console log  I am the arguments length  I am context excution spacific     arguments length   x000D  console log  I am being called From      function from    x000D    x000D   x000D     arguments 3 x000D  function parent    x000D  properties 1 2 3   x000D    x000D   x000D    arguments length 3 because execution spacific x000D  parent    x000D   x000D   x000D    Although it can be indexed like an array as you can see in this example     x000D   x000D  function add    x000D   x000D  var sum 0  x000D   x000D  for var i 0  i lt  arguments length i     x000D   x000D  sum   sum   arguments i   x000D   x000D    x000D   x000D  return sum  x000D   x000D    x000D   x000D  console log add 1 2 3    x000D   x000D   x000D    However  the Arguments object is not an array and does not have any other properties other than length   You can convert the arguments object into an array at which point you can access the Arguments object    There are many ways you can access the arguments object inside a function body  and these include     you can call the Array prototoype slice call method    Array prototype slice call arguments     x000D   x000D  function giveMeArgs arg1 arg2   x000D   x000D  var args   Array prototype slice call arguments   x000D  return args x000D    x000D   x000D  console log  giveMeArgs 1 2    x000D   x000D   x000D     you can use the array literal       slice call arguments     x000D   x000D  function giveMeArgs arg1 arg2   x000D   x000D  var args      slice call arguments   x000D   x000D  return args  x000D   x000D    x000D   x000D  console log  giveMeArgs 1 2     x000D   x000D   x000D     you can use Rest        x000D   x000D  function giveMeArgs    args   x000D   x000D  return args  x000D   x000D    x000D   x000D  console log giveMeArgs 1 2   x000D   x000D   x000D     you can use spread          x000D   x000D  function giveMeArgs    x000D   x000D  var args       arguments   x000D  return args  x000D   x000D    x000D   x000D  console log giveMeArgs 1 2    x000D   x000D   x000D     you can use Array from      x000D   x000D  function giveMeArgs    x000D   x000D  var args   Array from arguments   x000D   x000D  return args  x000D   x000D    x000D   x000D  console log giveMeArgs 1 2    x000D   x000D   x000D

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ES6 using rest parameters  If you are able to use ES6 you can use   Rest Parameters   x000D   x000D  function sortArgs    args    x000D    return args sort function  a  b    return a - b      x000D    x000D   x000D  document body innerHTML   sortArgs 12  4  6  8  toString    x000D   x000D   x000D    As you can read in the link     The rest parameter syntax allows us to represent an indefinite number of arguments as an array    If you are curious about the     syntax  it is called Spread Operator and you can read more here   ES6 using Array from    Using Array from    x000D   x000D  function sortArgs     x000D    return Array from arguments  sort function  a  b    return a - b      x000D    x000D   x000D  document body innerHTML   sortArgs 12  4  6  8  toString    x000D   x000D   x000D    Array from simply convert Array-like or Iterable objects into Array instances        ES5  You can actually just use Array s slice function on an arguments object  and it will convert it into a standard JavaScript array  You ll just have to reference it manually through Array s prototype   function sortArgs         var args   Array prototype slice call arguments       return args sort        Why does this work  Well  here s an excerpt from the ECMAScript 5 documentation itself      NOTE  The slice function is intentionally generic  it does not require that its this value be an Array object  Therefore it can be transferred to other kinds of objects for use as a method  Whether the slice function can be applied successfully to a host object is implementation-dependent    Therefore  slice works on anything that has a length property  which arguments conveniently does     If Array prototype slice is too much of a mouthful for you  you can abbreviate it slightly by using array literals   var args      slice call arguments     However  I tend to feel that the former version is more explicit  so I d prefer it instead  Abusing the array literal notation feels hacky and looks strange

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x000D   x000D  function sortArgs    args    x000D    return args sort function  a  b    return a - b      x000D    x000D   x000D  document body innerHTML   sortArgs 1  2  3  4  toString    x000D   x000D   x000D

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Use   function sortArguments       return arguments length     1    arguments 0                      Array apply null  arguments  sort        Array arg1  arg2       returns  arg1  arg2        Array str1  returns  str1   Array num1  returns an array that has num1 elements  You must check number of arguments   Array slice version  slower    function sortArguments       return Array prototype slice call arguments  sort        Array push version  slower  faster than slice    function sortArguments       var args         Array prototype push apply args  arguments     return args sort        Move version  slower  but small size is faster    function sortArguments       var args         for  var i   0  i  lt  arguments length    i      args i    arguments i     return args sort        Array concat version  slowest    function sortArguments       return Array prototype concat apply     arguments  sort

[javascript] How can I convert the "arguments" object to an array in JavaScript?

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