javascript how sort array of objects by two rule?

Question

I have a list of object like this:

 [
      {"groups":["aaa"]},
      {"groups":["bbb"]},
      {"groups":["ccc"]},
      {"groups":["ddd"]},
      {"groups":["eee"]},
      {"groups":["fff"]},
      {"groups":["ggg"]},
      {"groups":["hhh"]},
      {"groups":["iii"]},
      {"groups":["mmm", "mmm"]}
      {"groups":["lll", "lll"]}
];

i want put all object with more that one groups at the end of the list in alphabetical order and keep the others with one groups, at beginning of the list without change the original order.

This is my code

var list = [
  {"groups":["aaa"]},
  {"groups":["bbb"]},
  {"groups":["ccc"]},
  {"groups":["ddd"]},
  {"groups":["eee"]},
  {"groups":["fff"]},
  {"groups":["ggg"]},
  {"groups":["hhh"]},
  {"groups":["iii"]},
  {"groups":["mmm", "mmm"]},
  {"groups":["lll", "lll"]}
];

list.sort(function(a, b){
        var aIsGroup = (a.groups.length > 1);
        var bIsGroup = (b.groups.length > 1);

        if (aIsGroup && !bIsGroup) {
            return 1;
        } else if (!aIsGroup && bIsGroup) {
            return -1;
        } else if(aIsGroup && bIsGroup){
            return a.groups[0].toLowerCase().localeCompare(b.groups[0].toLowerCase());
        }
        return 0;
});

console.log(list);

You can see in the snippet the current output, but the expected output is:

[
  {
    "groups": [
      "aaa"
    ]
  },
  {
    "groups": [
      "bbb"
    ]
  },
  {
    "groups": [
      "ccc"
    ]
  },
  {
    "groups": [
      "ddd"
    ]
  },
  {
    "groups": [
      "eee"
    ]
  },
  {
    "groups": [
      "fff"
    ]
  },
  {
    "groups": [
      "ggg"
    ]
  },
  {
    "groups": [
      "hhh"
    ]
  },
  {
    "groups": [
      "iii"
    ]
  },
  {
    "groups": [
      "lll",
      "lll"
    ]
  },
  {
    "groups": [
      "mmm",
      "mmm"
    ]
  }
]

Javascript's `sort` doesn't promise a stable sorting. Any elements that are "equal" have an undefined order. See the duplicate for implementing a *stable* sort. — deceze, Aug 30 '18 at 08:16
Why not filter the entries with multiple groups first, remove them from the original array and then append them? — connexo, Aug 30 '18 at 08:21
Change `a.groups.length > 1` to `a.groups.length > 0` and `b.groups.length > 1` to `b.groups.length > 0` — morteza ataiy, Aug 30 '18 at 08:23
@WhiteMaple Because the question is closed and no further answers can be added. — connexo, Aug 30 '18 at 08:25

jonatjano · Answer 1 · 2018-08-30T08:22:03.207

0

as @deceze said in comment

Javascript's sort doesn't promise a stable sorting. Any elements that are "equal" have an undefined order. See the duplicate for implementing a stable sort

but you can do this to keep them in the same order as their original order (a stable sort)

var list = [
  {"groups":["aaa"]},
  {"groups":["bbb"]},
  {"groups":["ccc"]},
  {"groups":["mmm", "mmm"]},
  {"groups":["ddd"]},
  {"groups":["fff"]},
  {"groups":["eee"]},
  {"groups":["ggg"]},
  {"groups":["hhh"]},
  {"groups":["iii"]},
  {"groups":["lll", "lll"]}
];

list.sort(function(a, b){
        var aIsGroup = (a.groups.length > 1);
        var bIsGroup = (b.groups.length > 1);

        if (aIsGroup && !bIsGroup) {
            return 1;
        } else if (!aIsGroup && bIsGroup) {
            return -1;
        } else if(aIsGroup && bIsGroup) {
            return a.groups[0].toLowerCase().localeCompare(b.groups[0].toLowerCase());
        }
        // keep in the same order
        return (list.indexOf(a) < list.indexOf(b)) ? -1 : 1;
});

console.log(list);

edited Aug 30 '18 at 08:22

answered Aug 30 '18 at 08:14

jonatjano

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I'm not sure the criterion is to sort them lexically, but rather they should retain their original order (i.e. *stable sort*). – deceze Aug 30 '18 at 08:15
@deceze you may be correct need to ask op – jonatjano Aug 30 '18 at 08:16
@deceze rereading the question you're correct – jonatjano Aug 30 '18 at 08:17
@deceze, thanks but i want the alphabetical order only if `(a.groups.length > 1) && (b.groups.length > 1)` – ar099968 Aug 30 '18 at 08:19
@ar099968 edited ;) `fff` and `eee` are mixed because I mixed them when declaring array to show no lexical on monoelement – jonatjano Aug 30 '18 at 08:22

javascript how sort array of objects by two rule?

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