How to sort an associative array by its values in Javascript

Question

I have the associative array  array  quot sub2 quot     1  array  quot sub0 quot     -1  array  quot sub1 quot     0  array  quot sub3 quot     1  array  quot sub4 quot     0   What is the most elegant way to sort  descending  by its values where the result would be an array with the respective indices in this order  sub2  sub3  sub1  sub4  sub0

User · Answer

The best approach for the specific case here, in my opinion, is the one commonpike suggested. A little improvement I'd suggest that works in modern browsers is:

// aao is the "associative array" you need to "sort"
Object.keys(aao).sort(function(a,b){return aao[b]-aao[a]});

This could apply easily and work great in the specific case here so you can do:

let aoo={};
aao["sub2"]=1;
aao["sub0"]=-1;
aao["sub1"]=0;
aao["sub3"]=1;
aao["sub4"]=0;

let sk=Object.keys(aao).sort(function(a,b){return aao[b]-aao[a]});

// now you can loop using the sorted keys in `sk` to do stuffs
for (let i=sk.length-1;i>=0;--i){
 // do something with sk[i] or aoo[sk[i]]
}

Besides of this, I provide here a more "generic" function you can use to sort even in wider range of situations and that mixes the improvement I just suggested with the approaches of the answers by Ben Blank (sorting also string values) and PopeJohnPaulII (sorting by specific object field/property) and lets you decide if you want an ascendant or descendant order, here it is:

// aao := is the "associative array" you need to "sort"
// comp := is the "field" you want to compare or "" if you have no "fields" and simply need to compare values
// intVal := must be false if you need comparing non-integer values
// desc := set to true will sort keys in descendant order (default sort order is ascendant)
function sortedKeys(aao,comp="",intVal=false,desc=false){
  let keys=Object.keys(aao);
  if (comp!="") {
    if (intVal) {
      if (desc) return keys.sort(function(a,b){return aao[b][comp]-aao[a][comp]});
      else return keys.sort(function(a,b){return aao[a][comp]-aao[a][comp]});
    } else {
      if (desc) return keys.sort(function(a,b){return aao[b][comp]<aao[a][comp]?1:aao[b][comp]>aao[a][comp]?-1:0});
      else return keys.sort(function(a,b){return aao[a][comp]<aao[b][comp]?1:aao[a][comp]>aao[b][comp]?-1:0});
    }
  } else {
    if (intVal) {
      if (desc) return keys.sort(function(a,b){return aao[b]-aao[a]});
      else return keys.sort(function(a,b){return aao[a]-aao[b]});
    } else {
      if (desc) return keys.sort(function(a,b){return aao[b]<aao[a]?1:aao[b]>aao[a]?-1:0});
      else return keys.sort(function(a,b){return aao[a]<aao[b]?1:aao[a]>aao[b]?-1:0});
    }
  }
}

You can test the functionalities trying something like the following code:

let items={};
items['Edward']=21;
items['Sharpe']=37;
items['And']=45;
items['The']=-12;
items['Magnetic']=13;
items['Zeros']=37;
//equivalent to:
//let items={"Edward": 21, "Sharpe": 37, "And": 45, "The": -12, ...};

console.log("1: "+sortedKeys(items));
console.log("2: "+sortedKeys(items,"",false,true));
console.log("3: "+sortedKeys(items,"",true,false));
console.log("4: "+sortedKeys(items,"",true,true));
/* OUTPUT
1: And,Sharpe,Zeros,Edward,Magnetic,The
2: The,Magnetic,Edward,Sharpe,Zeros,And
3: The,Magnetic,Edward,Sharpe,Zeros,And
4: And,Sharpe,Zeros,Edward,Magnetic,The
*/

items={};
items['k1']={name:'Edward',value:21};
items['k2']={name:'Sharpe',value:37};
items['k3']={name:'And',value:45};
items['k4']={name:'The',value:-12};
items['k5']={name:'Magnetic',value:13};
items['k6']={name:'Zeros',value:37};

console.log("1: "+sortedKeys(items,"name"));
console.log("2: "+sortedKeys(items,"name",false,true));
/* OUTPUT
1: k6,k4,k2,k5,k1,k3
2: k3,k1,k5,k2,k4,k6
*/

As I already said, you can loop over sorted keys if you need doing stuffs

let sk=sortedKeys(aoo);
// now you can loop using the sorted keys in `sk` to do stuffs
for (let i=sk.length-1;i>=0;--i){
 // do something with sk[i] or aoo[sk[i]]
}

Last, but not least, some useful references to Object.keys and Array.sort

User · Answer

Javascript doesn t have  associative arrays  the way you re thinking of them   Instead  you simply have the ability to set object properties using array-like syntax  as in your example   plus the ability to iterate over an object s properties   The upshot of this is that there is no guarantee as to the order in which you iterate over the properties  so there is nothing like a sort for them   Instead  you ll need to convert your object properties into a  true  array  which does guarantee order    Here s a code snippet for converting an object into an array of two-tuples  two-element arrays   sorting it as you describe  then iterating over it   var tuples        for  var key in obj  tuples push  key  obj key      tuples sort function a  b        a   a 1       b   b 1        return a  lt  b   -1    a  gt  b   1   0        for  var i   0  i  lt  tuples length  i          var key   tuples i  0       var value   tuples i  1           do something with key and value     You may find it more natural to wrap this in a function which takes a callback    x000D   x000D  function bySortedValue obj  callback  context    x000D    var tuples       x000D   x000D    for  var key in obj  tuples push  key  obj key     x000D   x000D    tuples sort function a  b    x000D      return a 1   lt  b 1    1   a 1   gt  b 1    -1   0 x000D        x000D   x000D    var length   tuples length  x000D    while  length--  callback call context  tuples length  0   tuples length  1    x000D    x000D   x000D  bySortedValue   x000D    foo  1  x000D    bar  7  x000D    baz  3 x000D     function key  value    x000D    document getElementById  res   innerHTML       key     value  lt br gt   x000D      x000D   lt p id  res  gt Result  lt br  gt  lt br  gt  lt p gt  x000D   x000D   x000D

User · Answer

Here is a variation of ben blank s answer  if you don t like tuples     This saves you a few characters   var keys       for  var key in sortme      keys push key      keys sort function k0  k1      var a   sortme k0     var b   sortme k1     return a  lt  b   -1    a  gt  b   1   0        for  var i   0  i  lt  keys length    i      var key   keys i     var value   sortme key        Do something with key and value

User · Answer

There really isn t any such thing as an  associative array  in JavaScript  What you ve got there is just a plain old object   They work kind-of like associative arrays  of course  and the keys are available but there s no semantics around the order of keys   You could turn your object into an array of objects  key value pairs  and sort that   function sortObj object  sortFunc      var rv         for  var k in object        if  object hasOwnProperty k   rv push  key  k  value   object k           rv sort function o1  o2        return sortFunc o1 key  o2 key           return rv      Then you d call that with a comparator function

User · Answer

Continued discussion  amp  other solutions covered at How to sort an  associative  array by value  with the best solution  for my case  being by saml  quoted below    Arrays can only have numeric indexes   You d need to rewrite this as either an Object  or an Array of Objects   var status   new Array    status push  name   BOB   val  10    status push  name   TOM   val  3    status push  name   ROB   val  22    status push  name   JON   val  7      If you like the status push method  you can sort it with   status sort function a b        return a val - b val

User · Answer

i use   each of jquery but you can make it with a for loop  an improvement is this              ArraySort array             Sort an array                     ArraySort   function array  sortFunc                 var tmp                     var aSorted                   var oSorted                    for  var k in array                    if  array hasOwnProperty k                        tmp push  key  k  value   array k                                    tmp sort function o1  o2                        return sortFunc o1 value  o2 value                                                         if Object prototype toString call array        object Array                         each tmp  function index  value                         aSorted push value value                                           return aSorted                                                      if Object prototype toString call array        object Object                         each tmp  function index  value                         oSorted value key  value value                                                               return oSorted                                           So now you can do      console log  ArraySort        var arr1    4 3 6 1 2 8 5 9 9       var arr2     a  4   b  3   c  6   d  1   e  2   f  8   g  5   h  9       var arr3    a   green   b   brown   c   blue   d   red        var result1   ArraySort arr1  function a b  return a-b        var result2   ArraySort arr2  function a b  return a-b        var result3   ArraySort arr3  function a b  return a gt b        console log result1       console log result2              console log result3

User · Answer

commonpike s answer is  the right one   but as he goes on to comment        most browsers nowadays just support Object keys     Yeah   Object keys   is WAY better    But what s even better  Duh  it s it in coffeescript   sortedKeys    x  - gt  Object keys x  sort  a b  - gt  x a  - x b   sortedKeys    a     1    b     3    c     4    d    -1         d    a    b    c

User · Answer

No unnecessary complication required     function sortMapByValue map        var tupleArray           for  var key in map  tupleArray push  key  map key         tupleArray sort function  a  b    return a 1  - b 1          return tupleArray

User · Answer

Just so it s out there and someone is looking for tuple based sorts   This will compare the first element of the object in array  than the second element and so on  i e in the example below  it will compare first by  a   then by  b  and so on   let arr          a 1  b 2  c 3        a 3  b 5  c 1        a 2  b 3  c 9        a 2  b 5  c 9        a 2  b 3  c 10         function getSortedScore obj        var keys            for var key in obj 0   keys push key       return obj sort function a b           for  var i in keys                let k   keys i               if  a k -b k   gt  0  return -1              else if  a k -b k   lt  0  return 1              else continue                        console log getSortedScore arr     OUPUTS       a  3  b  5  c  1        a  2  b  5  c  9        a  2  b  3  c  10        a  2  b  3  c  9        a  1  b  2  c  3

User · Answer

Instead of correcting you on the semantics of an  associative array   I think this is what you want   function getSortedKeys obj        var keys   keys   Object keys obj       return keys sort function a b  return obj b -obj a         for really old browsers  use this instead   function getSortedKeys obj        var keys       for var key in obj  keys push key       return keys sort function a b  return obj b -obj a         You dump in an object  like yours  and get an array of the keys - eh properties - back  sorted descending by the  numerical  value of the  eh  values of the  eh  object   This only works if your values are numerical  Tweek the little function a b  in there to change the sorting mechanism to work ascending  or work for string values  for example   Left as an exercise for the reader

[javascript] How to sort an associative array by its values in Javascript?

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