Sort an array of objects if property exists

Question

I have an array of objects. Out of each of these objects onle few of them have a property and I want to sort the array putting those objects at top which have that property.

Ex -

arr= [{key1: "obj1val1", key2 :"obj1val2"}, 
      {key2 :"obj2val2"}, 
      {key1: "obj3val3", key2 :"obj3val3"},
      {key2 :"obj4val1"},
      {key1: "obj5val1", key2 :"obj5val2"}
]

Sorted by key1

Expected Result - [{key1: "obj1val1", key2 :"obj1val2"}, 
                   {key1: "obj3val3", key2 :"obj3val3"},
                   {key1: "obj5val1", key2 :"obj5val2"}, 
                   {key2 :"obj2val2"}, 
                   {key2 :"obj4val1"}]

I have tried below approach-

sort : function(arr) {
              var copyArr = arr.slice();
              var newArr = [];
              for(var i=0; i<arr.length; i++){
                if(arr[i].key1){
                  newArr.push(arr[i]);
                    copyArr.splice(i, 1);
                }
              }
              Array.prototype.push.apply(newArr, copyArr);
              return newArr;
            }

Not exactly but I see discrepancy from the above approach. For a array bigger length, some of the objects which have key1 are not moved to top. Can this be done by internal sort method of javascript? If yes, how will the custom function compare ?

Can only support ES5 methods.

Do you actually want to sort them by comparing all of them with each other, or do you want to keep the order but move those with the property to the top? In the latter case, don't use sort. — Bergi
– Bergi, Commented Sep 22, 2018 at 21:40
@Bergi That is why I have copied the original array and spliced the copied array. I want to keep the order but move the property to top — RahulB
– RahulB, Commented Sep 22, 2018 at 21:41
Still, the indices of the other elements change when you splice out one element. — Bergi
– Bergi, Commented Sep 22, 2018 at 21:43
Just use var withProp = [], withoutProp = []; … if ("key1" in arr[i]) withProp.push(arr[i]); else withoutProp.push(arr[i]); …. Don't copy anything beforehand or try to splice from it during a loop. — Bergi
– Bergi, Commented Sep 22, 2018 at 21:44

T.J. Crowder · Accepted Answer · 2018-09-22 21:44:00Z

16

Can this be done by internal sort method of javascript

Yes: Simply prefer the entry that has the property:

arr.sort(function(left, right) {
    return left.hasOwnProperty("key1") ? -1 : right.hasOwnProperty("key1") ? 1 : 0
});

Live Example:

var arr = [
    {key1: "obj1val1", key2 :"obj1val2"}, 
    {key2 :"obj2val2"}, 
    {key1: "obj3val3", key2 :"obj3val3"},
    {key2 :"obj4val1"},
    {key1: "obj5val1", key2 :"obj5val2"}
];
arr.sort(function(left, right) {
    return left.hasOwnProperty("key1") ? -1 : right.hasOwnProperty("key1") ? 1 : 0
});
console.log(arr);

If you also want to sort by that property's value:

arr.sort(function(left, right) {
    var leftHas = left.hasOwnProperty("key1");
    var rightHas = right.hasOwnProperty("key1");
    if (leftHas && rightHas) {
      return left.key1.localeCompare(right.key1);
    }
    return leftHas ? -1 : rightHas ? 1 : 0;
});

Live Example:

var arr = [
    {key1: "obj1val1", key2 :"obj1val2"}, 
    {key2 :"obj2val2"}, 
    {key1: "obj3val3", key2 :"obj3val3"},
    {key2 :"obj4val1"},
    {key1: "obj5val1", key2 :"obj5val2"}
];
arr.sort(function(left, right) {
    var leftHas = left.hasOwnProperty("key1");
    var rightHas = right.hasOwnProperty("key1");
    if (leftHas && rightHas) {
      return left.key1.localeCompare(right.key1);
    }
    return leftHas ? -1 : rightHas ? 1 : 0;
});
console.log(arr);

edited Sep 22, 2018 at 21:44

answered Sep 22, 2018 at 21:42

T.J. Crowder

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3 Comments

RahulB Over a year ago

Hi TJ..can you share an ES5 version of this answer?

T.J. Crowder Over a year ago

@RahulB - Wow, second nature to use arrow functions. :-) Done.

RahulB Over a year ago

Gosh, I did wrote this logic but messed up the return statements in the ternary. Neat solution. Should have reached SO a little earlier, wasted half of my sleeping time. Thanks TJ

Steven Spungin · Accepted Answer · 2018-09-22 21:46:47Z

1

Here is a working snippet that gives your requested result and is easily extended. It uses the native array sort.

arr = [{
    key1: "obj1val1",
    key2: "obj1val2"
  },
  {
    key2: "obj2val2"
  },
  {
    key1: "obj3val3",
    key2: "obj3val3"
  },
  {
    key2: "obj4val1"
  },
  {
    key1: "obj5val1",
    key2: "obj5val2"
  }
]

const sorted = arr.sort((a, b) => {
  const k1 = a.key1 === undefined ? 0 : 1
  const k2 = b.key1 === undefined ? 0 : 2
  return k2- k1
})
console.log(sorted)

answered Sep 22, 2018 at 21:46

Steven Spungin

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Comments

markb · Accepted Answer · 2018-09-22 21:43:46Z

0

A kind of janky way you can do it is:

arr.filter(obj => obj.hasOwnProperty('key1')).concat(arr.filter(obj => !obj.hasOwnProperty('key1')));

answered Sep 22, 2018 at 21:43

markb

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Comments

Ozan Honamlioglu · Accepted Answer · 2019-10-01 13:04:10Z

0

https://github.com/arraybrain/arraybrain

for complex array stuff, you can use it

answered Oct 1, 2019 at 13:04

Ozan Honamlioglu

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