Javascript sort array of objects by a boolean property

Question

See edit at end for actual problem.

Ok, I have this scenario:

a = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]

Then if I do this:

a.sort(function(a,b){return !a && b});

It gives me this:

[false, false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]

It's sorta doing a sort... but not quite... :(

How do I sort this array?

EDIT:

If you are wondering why I did not use just a.sort() is because my actual array is of objects, not a plain array like the one I posted. The real one has elements that look like [{xx:true},{xx:false},...]

If I do a.map(function(x){ return x?1:0 }).sort(function(a,b){return a>b}); does not work either... I think I might be doing something elementary wrong — PCoelho
– PCoelho, Commented Jun 30, 2013 at 5:25

Ashish Ranjan · Accepted Answer · 2017-11-22 15:12:41Z

358

a = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false];
    
    
    a.sort(function(x, y) {
        // true values first
        return (x === y)? 0 : x? -1 : 1;
        // false values first
        // return (x === y)? 0 : x? 1 : -1;
    });
    
    console.log(a);

You must return 0 when a and b both have the same value, -1 if a is true and 1 otherwise.

edited Nov 22, 2017 at 15:12

Ashish Ranjan

5,5533 gold badges20 silver badges40 bronze badges

answered Jun 30, 2013 at 5:26

c.P.u1

17.1k6 gold badges48 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

13 Comments

000 Over a year ago

Even shorter: a.sort(function(x, y) { return y - x });

c.P.u1 Over a year ago

@PCoelho, consider using Joe's solution. It works and is more concise.

Adam Moisa Over a year ago

@JoeFrambach Can you explain how that works or point me to a thread that explains the syntax for something like that?

Silvestre Herrera Over a year ago

@AdamMoisa Joe's solution works because of something called Type Coercion. Basically, the JS engine will notice you're trying to do a math operation (subtraction) on boolean values, so it'll convert false into 0 and true into 1.

technicolorenvy Over a year ago

@SilvestreHerrera No, there is no Type Coercion in the above example. According to the docs, developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…, the compareFunction needs to return -1,0, or 1, which will determine an element's position. The code example above uses nested ternary statements, which, in the case of the uncommented 'truthy values first' example says the following (in english) if x and y are strictly equal return 0, otherwise if x is true return -1 if not return 1;

|

sroes · Accepted Answer · 2018-03-20 13:51:34Z

86

To prevent implicit type conversion (which languages like TypeScript don't like), you can use Number() to explicitly convert the boolean to a number:

a = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false];
a.sort(function(x, y) {
   return Number(x) - Number(y);
});
console.log(a);

Or using arrow functions:

a = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false];
a.sort((x, y) => Number(x) - Number(y));
console.log(a);

edited Mar 20, 2018 at 13:51

answered Mar 20, 2018 at 13:13

sroes

15.1k1 gold badge58 silver badges75 bronze badges

2 Comments

JabbyPanda Over a year ago

One caveat: this sort compare function will not work with 'undefined` values in input array

foxiris Over a year ago

Or [true, false, true, false].sort((a, b) => +b - +a)

dandavis · Accepted Answer · 2013-06-30 05:53:13Z

51

a simpler way:

a = [{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false},{xx:true},{xx:false}];

a.sort(function(a,b){return a.xx-b.xx});

console.log(a);

you can call a.reverse() after the sort() if you want it sorted the other way..

EDIT: edited to reflect updated question of sorting an array of objects instead of an array of booleans.

edited Jun 30, 2013 at 5:53

answered Jun 30, 2013 at 5:35

dandavis

16.8k5 gold badges43 silver badges38 bronze badges

2 Comments

dandavis Over a year ago

@PranavNegandhi: what's wrong is that i answered the question before an edit re-defined it...

Yulian Over a year ago

Great, just if you want it sorted the other way, swap the places of a and b in the sort function, instead of calling reverse().

Kristjan Liiva · Accepted Answer · 2018-11-06 23:07:05Z

36

An array does not have any equal positions, so why not leave away the equals check, and always return either -1 or 1. This approach works well with TS.

a.sort(x => x ? -1 : 1)

Note: I am a bit concerned how this affects internals of the sort function, but it seems to do the trick.

If you want to reverse sort

a.sort(x => !x ? -1 : 1)

edited Nov 6, 2018 at 23:07

answered Oct 5, 2018 at 13:20

Kristjan Liiva

9,6593 gold badges28 silver badges26 bronze badges

3 Comments

ogostos Over a year ago

perfect solution, i like your minimalistic approach

Peter Over a year ago

In the case when you're sorting objects, this approach doesn't guarantee objects with equal property values (i.e. a.xx === b.xx) stay in the same order with respect to each other.

IonicMan Over a year ago

perfect, brother, very sexy solution

demo · Accepted Answer · 2022-06-06 10:22:40Z

31

Simple solution:

[true, false, true, false].sort((a, b) => b - a)

console.log([true, false, true, false].sort((a, b) => b - a));

edited Jun 6, 2022 at 10:22

demo

6,29519 gold badges84 silver badges162 bronze badges

answered Apr 18, 2018 at 9:28

Сергей Мисник

3113 silver badges4 bronze badges

1 Comment

mchl18 Over a year ago

huh, I did not expect that false - true === -1, thanks for this!

spedy · Accepted Answer · 2021-06-17 12:55:53Z

5

I also ran into this issue, here is my part, I hope it helps:

orders.sort((x, y) => {
   if (x === y) return 0;
   if (x) return -1;
   return 1;
});

answered Jun 17, 2021 at 12:55

spedy

2,37027 silver badges26 bronze badges

Comments

G. Frx · Accepted Answer · 2023-02-06 10:53:04Z

5

You can actually just do like the following:

const sortedData = data.sort(
  (a, b) => Number(b) - Number(a),
);

This solution is ok with Typescript has well since the conversion of boolean to number is explicit.

answered Feb 6, 2023 at 10:53

G. Frx

3,2504 gold badges25 silver badges34 bronze badges

Comments

dreamdeveloper · Accepted Answer · 2017-05-16 12:20:03Z

3

PFB the solution worked for me in Typescript Angular 2 as well,

  let a = [{aa:"1",xx:true},{aa:"10",xx:false},{aa:"2",xx:true},{aa:"11",xx:false},{aa:"3",xx:true},{aa:"12",xx:false},{aa:"4",xx:true},{aa:"13",xx:false},{aa:"5",xx:true},{aa:"14",xx:false},{aa:"6",xx:true},{aa:"15",xx:false},{aa:"7",xx:true},{aa:"16",xx:false},{aa:"8",xx:true},{aa:"17",xx:false},{aa:"9",xx:true},{aa:"18",xx:false}];

    //a.sort(function(a,b){return a.xx-b.xx});
    a.sort(function (x, y) {
        // true values first
        return (x.xx === y.xx) ? 0 : x ? -1 : 1;
        // false values first
        // return (x === y)? 0 : x? 1 : -1;
    });
    return JSON.stringify(a);

answered May 16, 2017 at 12:20

dreamdeveloper

1,2761 gold badge16 silver badges20 bronze badges

Comments

toddmo · Accepted Answer · 2020-05-10 18:58:15Z

2

I wanted to see if I could do it without using the ? : operator, just for fun.

Note

This works on all sortable data types (strings, numbers), not just raw booleans. I'm not sure if this is faster than ? : and it's more convoluted. I just get sick of conditionals so it's just personal preference.

  var b = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]
  .sort((a,b) => Number(a > b) * 2 - 1);

I can turn that into a utility function and give it a meaningful name:

  var sortOrder = {
    asc: (a,b) => Number(a > b) * 2 - 1,
    desc: (a,b) => Number(a < b) * 2 - 1
  }

so then I can:

  var b = [false, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]
  .sort(sortOrder.asc);

answered May 10, 2020 at 18:58

toddmo

22.7k14 gold badges105 silver badges120 bronze badges

1 Comment

Xavier Stévenne Over a year ago

Note that sort works with any number not just -1 or 1. Therefore you could use (a, b) => Number(a > b) - 0.5 to avoid a multiplication.

MattCochrane · Accepted Answer · 2018-04-09 23:47:24Z

1

A pretty simple solution for the comparison function is to check if a < b, this gives 0 or 1 when converted to a number. We then want to map 0 to -1 and 1 to 1. To do that you can just multiply by 2 then subtract 1.

data.sort(function (a, b) {
  return (a < b) * 2 - 1
}

or just

data.sort((a, b) => (a < b) * 2 - 1)

Problem sorted!

If any of your values are null they are treated as false (null*2 === 0) and any value that is undefined will become NaN (undefined*2 === NaN) which should make it last in either sort direction.

answered Apr 9, 2018 at 23:47

MattCochrane

3,1202 gold badges28 silver badges36 bronze badges

Comments

roy · Accepted Answer · 2022-01-07 17:49:05Z

1

A boolean array with enough entries to represent all transitions i.e. true to true, true to false, false to false, false to true.

var boolarray = [true, false, true, true, false, false, true]
boolarray.sort( (a,b) => !(a ^ b) ? 0 : a ? -1 : 1)

The sort inverts the xor of the inputs. If the inputs are the same then return 0, if they are not then, if the 'a' input is true 'b' must be false so return -1, and vice versa return 1.

'a' and 'b' booleans are sorted when they differ and are ignored when the same.

To use this method with objects just use the object member names for the sort arguments:

var objarray = [{xx:true}, {xx:false}, {xx:true}, {xx:true}, {xx:false}, {xx:false}, {xx:true}]
objarray.sort( (a,b) => !(a.xx ^ b.xx) ? 0 : a.xx ? -1 : 1)

answered Jan 7, 2022 at 17:49

roy

112 bronze badges

1 Comment

Ste Over a year ago

The '^' operator is not allowed for boolean types. Consider using '!==' instead.

chriscrossweb · Accepted Answer · 2020-03-10 10:07:07Z

0

I got typescript errors on the return (x.xx === y.xx) ? 0 : x ? -1 : 1;

This is my solution when you want to sort on a boolean property

this.mediaList.sort( (a: MediaAutosubscriptionModel, b: MediaAutosubscriptionModel) => {
    let status1: number = a.status === StatusEnum.ACTIVE ? 1 : 0;
    let status2: number = b.status === StatusEnum.ACTIVE ? 1 : 0;
    let comparison: number = 0;
    let direction: number = this.sortDirection === SortDirectionsEnum.ASC ? -1 : 1;
    if (status1 > status2) {
        comparison = direction;
    } else if (status1 < status2) {
        comparison = -1 * direction;
    }
        return comparison;
    });

answered Mar 10, 2020 at 10:07

chriscrossweb

3481 gold badge5 silver badges23 bronze badges

Comments

SIDDHANT JOHARI · Accepted Answer · 2021-03-17 08:23:20Z

0

a=[true,false,true,false,true];
 
a.sort(function(x, y) {
      a1=x?1:0
      b1=y?1:0
return a1-b1
    });

answered Mar 17, 2021 at 8:23

SIDDHANT JOHARI

821 silver badge5 bronze badges

Comments

Indrakant · Accepted Answer · 2022-08-17 05:38:27Z

0

Without using any ES6 function with time and space optimization -

const data = [false, true, true, true, false, false, false, true];
let lastElementUnchecked;
for(let i=0; i<data.length; i++){
    if(data[i] && lastElementUnchecked !== undefined){
        let temp = data[i];
        data[i] = data[lastElementUnchecked];
        data[lastElementUnchecked] = temp;
        i = lastElementUnchecked;
        lastElementUnchecked = undefined;
    }else{
        if(!data[i] && lastElementUnchecked === undefined){
            lastElementUnchecked = i;
        }
    }
}
console.log(data)

answered Aug 17, 2022 at 5:38

Indrakant

4216 silver badges10 bronze badges

Collectives™ on Stack Overflow

Javascript sort array of objects by a boolean property

14 Answers 14

13 Comments

2 Comments

2 Comments

3 Comments

1 Comment

Comments

Comments

Comments

1 Comment

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

14 Answers 14

13 Comments

2 Comments

2 Comments

3 Comments

1 Comment

Comments

Comments

Comments

1 Comment

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related