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},...]

Answer 1

 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.

Answer 2

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.

Answer 3

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);

Answer 4

简单的解决方案：

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

Answer 5

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)

Answer 6

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);

Answer 7

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.

Answer 8

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);

Answer 9

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

Answer 10

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

Answer 11

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;
});

Answer 12

A boolean array with enough entries to represent all transitions ie 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)

Answer 13

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)